OFFSET
0,7
LINKS
Eric Weisstein's World of Mathematics, Centered Pentagonal Number
FORMULA
G.f.: 1/(1 - Sum_{k>=0} x^(5*k*(k+1)/2+1)).
MAPLE
h:= proc(n) option remember; `if`(n<0, 0, (t->
`if`(((t+1)*5*t+2)/2>n, t-1, t))(1+h(n-1)))
end:
a:= proc(n) option remember; `if`(n=0, 1,
add(a(n-((i+1)*5*i+2)/2), i=0..h(n)))
end:
seq(a(n), n=0..60); # Alois P. Heinz, Dec 28 2018
MATHEMATICA
nmax = 50; CoefficientList[Series[1/(1 - Sum[x^(5 k (k + 1)/2 + 1), {k, 0, nmax}]), {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 26 2018
STATUS
approved