The OEIS is supported by the many generous donors to the OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A338990 a(n) is the first prime p such that the sum of 2*n consecutive primes starting at p is (q-1)*q where q is prime, or 0 if there is no such p. 2
 19, 61, 17, 8581, 10883, 151, 2083, 21859, 11813, 443, 6779, 1531, 21559, 37781, 7529, 757, 29027, 2591, 12739, 1637, 491, 4759, 56269, 341179, 37441, 81547, 59, 229, 1814023, 363523, 12109, 21493, 247993, 248089, 3617, 357551, 3109, 138563, 66973, 100103, 6907, 44819, 136519, 2953, 13063, 31687 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..306 EXAMPLE a(3) = 17 because the sum of the 2*3=6 consecutive primes starting at 17 is 17+19+23+29+31+37 = 156 = 12*13 where 13 is prime. MAPLE N:= 10^5: P:= select(isprime, [2, seq(i, i=3..N, 2)]): S:= ListTools:-PartialSums([0, op(P)]): nP:= nops(S): f:= proc(n) local i;   for i from 1 to nP-n do     if issqr(1+4*(S[i+n]-S[i])) and isprime((sqrt(1+4*(S[i+n]-S[i]))+1)/2)then return P[i] fi   od;   FAIL end proc: R:= NULL: for i from 1 do   v:= f(2*i);   if v = FAIL then break fi; R:= R, v od: R; CROSSREFS Cf. A338985, A338989. Sequence in context: A270818 A206426 A211145 * A158521 A141897 A031384 Adjacent sequences:  A338987 A338988 A338989 * A338991 A338992 A338993 KEYWORD nonn AUTHOR J. M. Bergot and Robert Israel, Dec 20 2020 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 28 03:20 EST 2022. Contains 350654 sequences. (Running on oeis4.)