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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 (list; graph; refs; listen; history; text; internal format)
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, lim-n, s = sum(k=i, i+n, pr[k]); if (issquare(s), return (i)); ); return (0); } \\ Michel Marcus, Oct 16 2013
CROSSREFS
Cf. A064397 (2 primes), A076305 (3 primes), A072849 (4 primes), A166255 (70 primes), A166261 (120 primes).
Cf. A132955 (primes themselves), A132956 (squares=sums), A132957 (square roots of sums).
Sequence in context: A187799 A288935 A132714 * A105419 A288242 A289266
KEYWORD
nonn
AUTHOR
Michel Marcus, Oct 16 2013
STATUS
approved

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Last modified May 23 02:40 EDT 2024. Contains 372758 sequences. (Running on oeis4.)