A073411 cototient(x) - 1 where x are the odd semiprimes (i.e., x are odd terms in A001358).

2, 6, 8, 4, 12, 10, 14, 6, 18, 14, 20, 16, 24, 16, 20, 30, 18, 32, 22, 38, 26, 22, 10, 42, 44, 24, 48, 22, 32, 34, 54, 28, 12, 60, 62, 40, 26, 68, 34, 44, 28, 72, 46, 36, 74, 28, 50, 80, 30, 84, 32, 42, 56, 90, 46, 16, 98, 62, 34, 48, 102, 64, 104, 38, 108, 34, 110, 52, 70

Offset

1,1

Comments

If the Goldbach conjecture is true, all even numbers appear at least once in the sequence since pq - phi(pq) - 1 = p + q.

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Formula

a(n) = A051953(A046315(n)) - 1. - Michel Marcus, Jul 30 2017; corrected Dec 29 2020

Mathematica

Map[# - EulerPhi@ # - 1 &, Select[Range[1, 335, 2], PrimeOmega # == 2 &]] (* Michael De Vlieger, Jul 30 2017 *)

Prog

(PARI) lista(nn) = forstep(n=1, nn, 2, if (bigomega(n)==2, print1(n-eulerphi(n)-1, ", "))); \\ Michel Marcus, Jul 30 2017

Crossrefs

Cf. A001358 (semiprimes), A046315 (odd semiprimes), A051953 (cototient).

Sequence in context: A276709 A115317 A117932 * A121862 A095677 A011045

Adjacent sequences: A073408 A073409 A073410 * A073412 A073413 A073414

Keyword

easy,nonn

Author

Benoit Cloitre, Aug 23 2002

Status

approved