A228588 Starting from a(1)=1, a(n) is the minimum integer greater than a(n-1) such that a(n)+a(n-1) and a(n)*a(n-1)+1 are both primes.

1, 2, 3, 4, 7, 10, 13, 24, 43, 46, 51, 56, 75, 76, 91, 102, 109, 132, 145, 166, 171, 176, 177, 196, 201, 208, 211, 228, 239, 248, 255, 286, 291, 296, 303, 314, 327, 346, 393, 430, 433, 454, 457, 480, 503, 506, 527, 534, 557, 594, 619, 630, 659, 708, 719, 728

Offset

1,2

Comments

Terms are alternately odd and even.

Links

Paolo P. Lava, Table of n, a(n) for n = 1..1000

Example

a(9)=43 and 43+44=87, 43+45=88 are not primes but 43+46=89 is prime and also 43*46+1=1979. Thus a(10)=51.

Maple

with(numtheory); P:=proc(q) local a, b, n; a:=1; b:=0; print(a);
for n from 1 to q do while not isprime(a+b) and not isprime (a*b+1) do
b:=b+2; od; print(b); a:=b; b:=b+1; od; print(); end: P(10^4);

Crossrefs

Cf. A228589, A228590.

Sequence in context: A333615 A329774 A081942 * A189720 A072958 A353837

Adjacent sequences: A228585 A228586 A228587 * A228589 A228590 A228591

Keyword

nonn

Author

Paolo P. Lava, Aug 27 2013

Status

approved