A063685 Numbers k such that !k + phi(k) - 1 is prime.

2, 3, 4, 5, 11, 20, 85, 212, 4925

Offset

1,1

Comments

a(10) > 5000. - J.W.L. (Jan) Eerland, Nov 19 2022

a(10) > 13469. - J.W.L. (Jan) Eerland, Nov 20 2022

a(10) > 30000. - Michael S. Branicky, Aug 19 2024

Links

Table of n, a(n) for n=1..9.

Mathematica

n=1; Monitor[Parallelize[While[True, If[PrimeQ[Sum[Factorial[k], {k, 0, n-1}]+EulerPhi[n]-1], Print[n]]; n++]; n], n] (* J.W.L. (Jan) Eerland, Nov 19 2022 *)

Prog

(PARI) f(n) = sum(k=0, n-1, k!); \\ A003422
for(n=1, 10^6, if(isprime(f(n)+eulerphi(n)-1), print(n)))

Crossrefs

Cf. A003422.

Sequence in context: A118968 A073528 A116067 * A006481 A118597 A083160

Adjacent sequences: A063682 A063683 A063684 * A063686 A063687 A063688

Keyword

nonn,more

Author

Jason Earls, Aug 22 2001

Extensions

a(9) from J.W.L. (Jan) Eerland, Nov 19 2022

Status

approved