A231099 Primes expressible as phi(sigma(n)) + sigma(phi(n)), in order of their occurrence.

2, 3, 5, 7, 13, 19, 23, 37, 47, 31, 67, 109, 71, 79, 139, 127, 139, 163, 227, 199, 443, 379, 313, 271, 547, 367, 619, 547, 593, 643, 523, 739, 619, 1093, 883, 691, 907, 787, 1153, 787, 787, 787, 1867, 1327, 1987, 1231, 1487, 1487, 2731, 2659, 2551, 4327, 4231

Offset

1,1

Links

K. D. Bajpai, Table of n, a(n) for n = 1..3500

Example

a(6)= 19: phi(sigma(12)) + sigma(phi(12))= 12+7= 19 which is prime.
a(9)= 47: phi(sigma(19)) + sigma(phi(19))= 8+39= 47 which is prime.

Maple

with(numtheory): KD:= proc() local a; a:= phi(sigma(n))+sigma(phi(n)); if isprime(a) then return (a) : fi; end: seq(KD(), n=1..10000);

Crossrefs

Cf. A062401 (phi(sigma(n))).

Cf. A062402 (sigma(phi(n))).

Sequence in context: A319126 A134266 A233043 * A062252 A153800 A362777

Adjacent sequences: A231096 A231097 A231098 * A231100 A231101 A231102

Keyword

nonn,less

Author

K. D. Bajpai, Nov 03 2013

Status

approved