

A256119


Least number p that is zero or an odd prime, such that n  p is a generalized pentagonal number.


2



0, 0, 0, 3, 3, 0, 5, 0, 3, 7, 3, 11, 0, 11, 7, 0, 11, 5, 3, 7, 5, 19, 0, 11, 17, 3, 0, 5, 13, 3, 23, 5, 17, 7, 19, 0, 29, 11, 3, 13, 0, 19, 7, 3, 29, 5, 11, 7, 13, 23, 43, 0, 17, 13, 3, 29, 5, 0, 7, 19, 3, 59, 5, 23, 7, 43, 31, 41, 11, 29, 0, 31, 37, 3, 17, 5, 19, 0, 43, 53, 3, 11, 5, 13, 7, 59, 29, 17, 11, 19, 13, 79, 0, 23, 17, 3, 19, 5, 41, 7, 0
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,4


COMMENTS

By the conjecture in A256071, a(n) always exists.


LINKS

ZhiWei Sun, Table of n, a(n) for n = 0..10000


EXAMPLE

a(21) = 19 since 21 is not a generalized pentagonal number, and 19 is the least odd prime p with 21  p a generalized pentagonal number.
a(26) = 0 since 26 = (4)*(3*(4)1)/2 is a generalized pentagonal number.


MATHEMATICA

Pen[n_]:=IntegerQ[Sqrt[24n+1]]
Do[If[Pen[n], Print[n, " ", 0]; Goto[aa]]; Do[If[Pen[nPrime[k]], Print[n, " ", Prime[k]]; Goto[aa]], {k, 2, PrimePi[n]}]; Label[aa]; Continue, {n, 0, 100}]


CROSSREFS

Cf. A000040, A001318, A256071.
Sequence in context: A140686 A116580 A096439 * A217552 A128046 A102899
Adjacent sequences: A256116 A256117 A256118 * A256120 A256121 A256122


KEYWORD

nonn


AUTHOR

ZhiWei Sun, Mar 15 2015


STATUS

approved



