A086505 a(n) is the n-th smallest prime p such that p+2n is also prime.

3, 7, 11, 23, 31, 29, 53, 73, 53, 89, 157, 73, 137, 199, 73, 281, 229, 127, 383, 229, 149, 389, 463, 193, 359, 547, 239, 467, 823, 197, 857, 883, 283, 809, 499, 389, 1013, 907, 421, 827, 1201, 373, 1151, 1231, 367, 1307, 1279, 577, 1229, 1009, 631, 1427, 1783

Offset

1,1

Comments

Note the patterns in the graph. These patterns depend on the number of prime factors of n: see color graph for different n's: n primes - black dots, n multiples of 3 - red dots, n multiples of 15 - green dots, n multiples of 105 - blue dots. - Zak Seidov, Nov 28 2013

Links

Zak Seidov, Table of n, a(n) for n = 1..10000

Zak Seidov, Color graph for different n's

Maple

N:= 10^4: # to get all terms before the first with a(n)+2*n > N
Primes:= select(isprime, {seq(2*i+1, i=1..N)}):
for n from 1 do
R:= Primes intersect map(`+`, Primes, -2*n);
if nops(R) < n then break fi;
A[n]:= R[n];
od:
seq(A[j], j=1..n-1); # Robert Israel, Aug 07 2014

Crossrefs

Cf. A020483, A231608.

Sequence in context: A111668 A112038 A097452 * A239227 A154427 A287459

Adjacent sequences: A086502 A086503 A086504 * A086506 A086507 A086508

Keyword

nonn

Author

Amarnath Murthy, Jul 29 2003

Extensions

Edited by Sam Alexander, Feb 26 2004

Status

approved