A079833 Define f(n) = n + tau(n), then a(n) = smallest prime of the type f(f(f...f(n)))).

2, 7, 5, 7, 7, 71, 71, 71, 71, 71, 13, 71, 19, 71, 19, 71, 19, 71, 71, 71, 71, 71, 71, 71, 71, 71, 31, 71, 31, 71, 37, 71, 37, 71, 43, 59, 43, 71, 43, 811, 43, 71, 59, 71, 59, 71, 811, 811, 811, 71, 59, 811, 59, 811, 59, 71, 61, 811, 61, 163, 73, 811, 73, 71, 73, 811, 73

Offset

1,1

Links

Table of n, a(n) for n=1..67.

Example

a(6) = 71 as f(6) = 10, f(10) = 14, f(14) = 18, f(18) = 24, f(24) = 32, f(32) = 38, f(38) = 42, f(42) = 50, f(50) = 56, f(56) = 64, f(64) = 64 +7 = 71.

Prog

(PARI) { a(n) = local(k, m); k=1; m=n; while(1, m=m+numdiv(m); if(isprime(m), return(m)); k++ ) } (Alekseyev)

Crossrefs

Cf. A079834.

Sequence in context: A097157 A181320 A195450 * A198737 A010593 A332322

Adjacent sequences: A079830 A079831 A079832 * A079834 A079835 A079836

Keyword

nonn

Author

Amarnath Murthy, Feb 12 2003

Extensions

More terms from Max Alekseyev, Apr 19 2005

Status

approved