A020643 a(n)-th squarefree is sum of first k squarefrees for some k.

1, 3, 5, 8, 12, 22, 36, 55, 77, 102, 133, 169, 187, 248, 296, 320, 343, 395, 483, 547, 652, 768, 809, 851, 893, 935, 1023, 1065, 1158, 1206, 1256, 1359, 1412, 1522, 1631, 1746, 1805, 1932, 1992, 2057, 2316, 2385, 2454, 2665, 2812, 2887, 3043, 3119, 3199, 3279

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

A005117(a(n)) = A013932(n). - Amiram Eldar, Aug 19 2025

Mathematica

With[{s = Select[Range[6000], SquareFreeQ]}, Position[s, #] & /@ Select[Accumulate[s], # <= s[[-1]] && SquareFreeQ[#] &] // Flatten] (* Amiram Eldar, Aug 19 2025 *)

Crossrefs

Cf. A005117, A013930, A013931, A013932.

Sequence in context: A147879 A147880 A276527 * A131354 A358767 A092360

Adjacent sequences: A020640 A020641 A020642 * A020644 A020645 A020646

Keyword

nonn

Author

N. J. A. Sloane, Renaud Lifchitz (100637.64(AT)CompuServe.COM), and David W. Wilson

Status

approved