A145397 Numbers not of the form m*(m+1)*(m+2)/6, the non-tetrahedral numbers.

2, 3, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78

Offset

1,1

Comments

Complement of A000292; A000040 is a subsequence.

Links

G. C. Greubel, Table of n, a(n) for n = 1..5000

Cristinel Mortici, Remarks on Complementary Sequences, Fibonacci Quart. 48 (2010), no. 4, 343-347.

Formula

A014306(a(n)) = 1; A023533(a(n)) = 0.

Mathematica

Select[Range[100], Binomial[Floor[Surd[6*# -1, 3]] +2, 3] != # &] (* G. C. Greubel, Feb 20 2022 *)

Prog

(PARI) is(n)=binomial(sqrtnint(6*n, 3)+2, 3)!=n \\ Charles R Greathouse IV, Feb 22 2017
(Magma) [n: n in [1..100] | Binomial(Floor((6*n-1)^(1/3))+2, 3) ne n ]; // G. C. Greubel, Feb 20 2022
(Sage) [n for n in (1..100) if binomial( floor( real_nth_root(6*n-1, 3) ) +2, 3) != n ] # G. C. Greubel, Feb 20 2022

Crossrefs

Cf. A000040, A000292, A014306, A023533.

Sequence in context: A268231 A039167 A247360 * A183570 A181092 A184526

Adjacent sequences: A145394 A145395 A145396 * A145398 A145399 A145400

Keyword

nonn

Author

Reinhard Zumkeller, Oct 14 2008

Extensions

Definition corrected by Ant King, Sep 20 2012

Status

approved