

A257717


a(n) is the smallest olddindexed prime not included earlier such that a(n) + a(n1) + a(n2) is a prime, beginning with a(1) = 5 and a(2) = 11.


3



5, 11, 31, 17, 23, 67, 41, 59, 73, 47, 103, 83, 97, 127, 149, 157, 137, 167, 283, 191, 179, 109, 211, 227, 313, 233, 197, 331, 241, 257, 379, 347, 307, 367, 389, 277, 353, 401, 439, 269, 509, 499, 419, 449, 571, 431, 487, 563, 461, 547, 523, 587, 599, 661, 607, 761, 631, 677
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OFFSET

1,1


COMMENTS

The union of A257716 and A257717 is A065091 (conjecture).


LINKS

Table of n, a(n) for n=1..58.


EXAMPLE

a(3) = 31 since a(1)+a(2) is 16 and 31, whose index equals 11, is the first oddindexed prime which meets the criteria. 16 + 7 = 23, a prime, but 7 is the 4th prime and therefore cannot be used.


MATHEMATICA

f[s_List] := Block[{p = s[[2]] + s[[1]], q = 17}, While[ !PrimeQ[p + q]  MemberQ[s, q], q = NextPrime[q, 2]]; Append[s, q]]; Nest[f, {5, 11}, 56]


PROG

(PARI) v=[5, 11]; n=1; while(n<100, p=prime(2*n1); if(isprime(v[#v]+v[#v1]+p)&&!vecsearch(vecsort(v), p), v=concat(v, p); n=0); n++); v \\ Derek Orr, May 13 2015


CROSSREFS

Cf. A073653, A257716, A257718.
Sequence in context: A209659 A266820 A114688 * A192194 A239842 A092963
Adjacent sequences: A257714 A257715 A257716 * A257718 A257719 A257720


KEYWORD

nonn


AUTHOR

Robert G. Wilson v, May 05 2015


STATUS

approved



