The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A338989 a(n) is the first prime p such that the sum of 2*n consecutive primes starting at p is q*(q+1) where q is prime, or 0 if there is no such p. 2
 5, 71, 3, 977, 37, 7829, 8681, 283, 14341, 37181, 31, 8839, 1181, 60901, 54727, 2579, 64901, 1248019, 43, 141803, 47, 29881, 991, 5, 881, 1603919, 31123, 18679, 174149, 74149, 11, 1328269, 925513, 447859, 61, 890969, 5867, 35759, 4093, 27239, 1549, 6551, 1901987, 4597, 64781, 307, 13121, 353 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..141 EXAMPLE a(3) = 3 because the sum of the 2*3=6 consecutive primes starting at 3 is 3+5+7+11+13+17 = 56 = 7*(7+1) where 7 is prime. a(4) = 977 because the sum of the 2*4=8 consecutive primes starting at 977 is 977+983+991+997+1009+1013+1019+1021 = 8010 = 89*(89+1) where 89 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, A338990. Sequence in context: A015502 A303291 A324229 * A101019 A056266 A248367 Adjacent sequences:  A338986 A338987 A338988 * A338990 A338991 A338992 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 December 9 09:37 EST 2021. Contains 349627 sequences. (Running on oeis4.)