

A230327


Index of smallest prime such that the sum of n consecutive primes starting with this specific prime is a square.


2



7, 6, 3, 42, 107, 6, 38, 1, 1631, 170, 38, 119, 5, 546, 78, 309, 85, 604, 199, 57, 270, 2, 3, 333, 45, 2, 178, 1708, 291, 2, 35, 72, 322, 19, 84, 5, 155, 346, 122, 2175, 1395, 24, 886, 2, 3108, 168, 14, 499, 340, 294, 156, 578, 325, 240, 115, 61, 283, 1035
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OFFSET

2,1


LINKS



EXAMPLE

a(2)=7 because 17+19 (2 terms) = 36 is a square, 17 being the 7th prime.
a(3)=6 because 13+17+19 (3 terms) =49 is a square, 13 being the 6th prime.


PROG

(PARI) a(n, lim=10^5) = {n ; pr = primes(lim); for (i = 1, limn, s = sum(k=i, i+n, pr[k]); if (issquare(s), return (i)); ); return (0); } \\ Michel Marcus, Oct 16 2013


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



