A026471 a(n) = least positive integer > a(n-1) and not of the form a(i) + a(j) + a(k) for 1 <= i < j < k <= n.

1, 2, 3, 4, 5, 13, 14, 15, 25, 26, 27, 37, 38, 48, 49, 50, 60, 61, 71, 72, 73, 83, 84, 94, 95, 96, 106, 107, 117, 118, 119, 129, 130, 140, 141, 142, 152, 153, 163, 164, 165, 175, 176, 186, 187, 188, 198, 199, 209, 210, 211, 221, 222, 232, 233, 234, 244, 245, 255

Offset

1,2

Links

Table of n, a(n) for n=1..59.

Wieb Bosma, Rene Bruin, Robbert Fokkink, Jonathan Grube, Anniek Reuijl, and Thian Tromp, Using Walnut to solve problems from the OEIS, arXiv:2503.04122 [math.NT], 2025.

Orion Shtrezi, The greedy 3-sumfree sequence S 1,g,g+1, arXiv:2606.17447 [math.CO], 2026.

Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,-1).

Formula

{1, 5, 13} union {n congruent 2, 3, 4, 14, 15 mod 23}, proved by Matthew Akeran. - Ralf Stephan, Nov 15 2004

G.f.: (9*x^11-7*x^10+9*x^8+7*x^5+x^4+x^3+x^2+x+1)*x/(x^6-x^5-x+1). - Alois P. Heinz, Aug 06 2018

Crossrefs

Cf. A003278, A033627, A075122, A075123.

Sequence in context: A367140 A369739 A101546 * A039039 A141484 A175303

Adjacent sequences: A026468 A026469 A026470 * A026472 A026473 A026474

Keyword

nonn,easy

Author

Clark Kimberling

Extensions

Edited by Floor van Lamoen, Sep 02 2002

Status

approved