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 A288631 Numbers that are the sum of two nonzero square pyramidal numbers (A000330). 3
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified August 8 18:48 EDT 2024. Contains 375023 sequences. (Running on oeis4.)