A118507 Larger of two consecutive Sophie Germain primes with the same digital sum.

131, 509, 719, 761, 2693, 3593, 3821, 4019, 4073, 4391, 4409, 4481, 4733, 5171, 6131, 6263, 6581, 6761, 7121, 7541, 7841, 9473, 9629, 10163, 10253, 10271, 10331, 10709, 11831, 12653, 12671, 13229, 13553, 14081, 14153, 14249, 14321, 15773, 15791, 16253, 17291

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

113 and 131 are consecutive Sophie Germain primes that have the same digital sum, hence 131 is in the sequence. - Michel Marcus, Dec 01 2013

Mathematica

Select[Partition[{#, Total[IntegerDigits[#]]}&/@Select[Prime[Range[2000]], PrimeQ[ 2#+1]&], 2, 1], #[[1, 2]] == #[[2, 2]]&][[;; , 2, 1]] (* Harvey P. Dale, Feb 20 2023 *)

Prog

(PARI) lista(nn) = {lastsd = 0; forprime(p=2, nn, if (isprime(2*p+1), digs = digits(p); sd = sum(i=1, #digs, digs[i]); if (sd == lastsd, print1(p, ", ")); lastsd = sd; ); ); } \\ Michel Marcus, Dec 01 2013

Crossrefs

Cf. A005384.

Sequence in context: A068680 A276255 A142555 * A105837 A142205 A142807

Adjacent sequences: A118504 A118505 A118506 * A118508 A118509 A118510

Keyword

base,nonn

Author

Luc Stevens (lms022(AT)yahoo.com), May 06 2006

Extensions

Missing term 6761 and more terms added by Michel Marcus, Dec 01 2013

Status

approved