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A259402
Pentagonal numbers (A000326) that are the sum of seven consecutive pentagonal numbers.
5
287, 532, 17145051, 32963672, 1106094475927, 2126616990876, 71358579001465427, 137196568515066592, 4603627364594444737551, 8851099419054387781412, 296998415728087428795555787, 571019827783678204813603176, 19160555787678205016722039960967
OFFSET
1,1
FORMULA
G.f.: -7*x*(1968*x^4+1813*x^3-195857*x^2+35*x+41) / ((x-1)*(x^2-254*x+1)*(x^2+254*x+1)).
EXAMPLE
287 is in the sequence because P(14) = 287 = 5+12+22+35+51+70+92 = P(2)+ ... +P(8).
MATHEMATICA
LinearRecurrence[{1, 64514, -64514, -1, 1}, {287, 532, 17145051, 32963672, 1106094475927}, 20] (* Harvey P. Dale, May 13 2022 *)
PROG
(PARI) Vec(-7*x*(1968*x^4+1813*x^3-195857*x^2+35*x+41)/((x-1)*(x^2-254*x+1)*(x^2+254*x+1)) + O(x^20))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Jun 26 2015
STATUS
approved