A288631 Numbers that are the sum of two nonzero square pyramidal numbers (A000330).

2, 6, 10, 15, 19, 28, 31, 35, 44, 56, 60, 69, 85, 92, 96, 105, 110, 121, 141, 145, 146, 154, 170, 182, 195, 205, 209, 218, 231, 234, 259, 280, 286, 290, 295, 299, 315, 340, 344, 376, 386, 390, 399, 408, 415, 425, 440, 476, 489, 507, 511, 520, 525, 536, 561, 570, 589, 597, 646, 651, 655, 664, 670, 680

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, Square Pyramidal Number

Index to sequences related to pyramidal numbers

Maple

M:= 20: # to get all terms <= A000330(M)
sqp:= [seq(k*(k+1)*(2*k+1)/6, k=1..M)]:
sort(convert(select(`<=`, {seq(seq(sqp[i]+sqp[j], j=1..i), i=1..M-1)}, sqp[M]), list)); # Robert Israel, Jun 12 2017

Mathematica

nmax = 700; f[x_] := Sum[x^(k (k + 1) (2 k + 1)/6), {k, 1, 20}]^2; Exponent[#, x] & /@ List @@ Normal[Series[f[x], {x, 0, nmax}]]

Crossrefs

Cf. A000330, A000404, A020756, A051533, A102795.

Sequence in context: A329657 A179777 A285959 * A276211 A190091 A343148

Adjacent sequences: A288628 A288629 A288630 * A288632 A288633 A288634

Keyword

nonn

Author

Ilya Gutkovskiy, Jun 12 2017

Status

approved