Implement Tribonacci, Tetranacci

src/oeis/A000045.ts

@@ -1,13 +1,12 @@
-// Fibonacci numbers
+// Fibonacci numbers: a(n) = a(n-1) + a(n-2) for n >= 2 with a(0) = 0 and a(1) = 1.
 export default function* A000045(): Generator<bigint> {
-  let previous = 0n,
-    current = 1n
-  yield previous
-  yield current
+  let a0 = 0n, a1 = 1n
+  yield a0
+  yield a1
   for (;;) {
-    const sum = current + previous
-    previous = current
-    current = sum
-    yield current
+    const sum = a0 + a1
+    a0 = a1
+    a1 = sum
+    yield a1
   }
 }

src/oeis/A000073.ts

@@ -1,45 +1,14 @@
 // Tribonacci numbers: a(n) = a(n-1) + a(n-2) + a(n-3) for n >= 3 with a(0) = a(1) = 0 and a(2) = 1.
 export default function* A000073(): Generator<bigint> {
-  for (const n of [
-    0n,
-    0n,
-    1n,
-    1n,
-    2n,
-    4n,
-    7n,
-    13n,
-    24n,
-    44n,
-    81n,
-    149n,
-    274n,
-    504n,
-    927n,
-    1705n,
-    3136n,
-    5768n,
-    10609n,
-    19513n,
-    35890n,
-    66012n,
-    121415n,
-    223317n,
-    410744n,
-    755476n,
-    1389537n,
-    2555757n,
-    4700770n,
-    8646064n,
-    15902591n,
-    29249425n,
-    53798080n,
-    98950096n,
-    181997601n,
-    334745777n,
-    615693474n,
-    1132436852n,
-  ]) {
-    yield n
+  let a0 = 0n, a1 = 0n, a2 = 1n
+  yield a0
+  yield a1
+  yield a2
+  for (;;) {
+    const sum = a0 + a1 + a2
+    a0 = a1
+    a1 = a2
+    a2 = sum
+    yield a2
   }
 }

src/oeis/A000078.ts

@@ -1,45 +1,16 @@
 // Tetranacci numbers: a(n) = a(n-1) + a(n-2) + a(n-3) + a(n-4) for n >= 4 with a(0) = a(1) = a(2) = 0 and a(3) = 1.
 export default function* A000078(): Generator<bigint> {
-  for (const n of [
-    0n,
-    0n,
-    0n,
-    1n,
-    1n,
-    2n,
-    4n,
-    8n,
-    15n,
-    29n,
-    56n,
-    108n,
-    208n,
-    401n,
-    773n,
-    1490n,
-    2872n,
-    5536n,
-    10671n,
-    20569n,
-    39648n,
-    76424n,
-    147312n,
-    283953n,
-    547337n,
-    1055026n,
-    2033628n,
-    3919944n,
-    7555935n,
-    14564533n,
-    28074040n,
-    54114452n,
-    104308960n,
-    201061985n,
-    387559437n,
-    747044834n,
-    1439975216n,
-    2775641472n,
-  ]) {
-    yield n
+  let a0 = 0n, a1 = 0n, a2 = 0n, a3 = 1n
+  yield a0
+  yield a1
+  yield a2
+  yield a3
+  for (;;) {
+    const sum = a0 + a1 + a2 + a3
+    a0 = a1
+    a1 = a2
+    a2 = a3
+    a3 = sum
+    yield a3
   }
 }