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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. 3
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 (list; graph; refs; listen; history; text; internal format)
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 A062426

Adjacent sequences:  A228585 A228586 A228587 * A228589 A228590 A228591

KEYWORD

nonn

AUTHOR

Paolo P. Lava, Aug 27 2013

STATUS

approved

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Last modified October 31 05:06 EDT 2020. Contains 338098 sequences. (Running on oeis4.)