OFFSET
1,1
COMMENTS
An integer q is a term iff q = p^(4*m+1), when p is prime of the form k^4 + 1 and m >= 0, then phi(q) = (k * (k^4+1)^m))^4. The primitive terms of this sequence are the primes of the form p = k^4 + 1, which are exactly in A037896.
EXAMPLE
a(14) = 1419857 = 17^5 and phi(1419857) = 34^4.
PROG
(PARI) isok(n) = isprimepower(n) && ispower(eulerphi(n), 4); \\ Michel Marcus, Apr 23 2019
(Magma) [n:n in [1..10000000]| #PrimeDivisors(n) eq 1 and IsPower(EulerPhi(n), 4)]; // Marius A. Burtea, May 09 2019
CROSSREFS
Cf. A054755 (idem with Euler's totient is square).
KEYWORD
nonn
AUTHOR
Bernard Schott, Apr 22 2019
STATUS
approved