A085382 Sum of p = prime(n) and largest prime divisor of p-1.

5, 7, 10, 16, 16, 19, 22, 34, 36, 36, 40, 46, 50, 70, 66, 88, 66, 78, 78, 76, 92, 124, 100, 100, 106, 120, 160, 112, 120, 134, 144, 154, 162, 186, 156, 170, 166, 250, 216, 268, 186, 210, 196, 204, 210, 218, 260, 340, 248, 262, 256, 246, 256, 259, 394, 336, 276, 300

Offset

2,1

Links

Table of n, a(n) for n=2..59.

Formula

a(n) = p + A006530(p-1) where p = prime(n).

Example

a(2) = prime(2) + gpf(prime(2) - 1) = 3 + gpf(2) = 3 + 2 = 5.

Prog

(PARI) cminuspm2(n) = \\ prime + maxprime of prime-1
{ forprime(x=5, n, forstep(p=x, 2, -1, if(isprime(p) & (x-1)%p==0, print1(x+p, ", "); break); ) ) }
(PARI) a(n) = my(p=prime(n)); p+vecmax(factor(p-1)[, 1]); \\ Michel Marcus, May 07 2024

Crossrefs

Cf. A006530, A023503, A274022.

Sequence in context: A196936 A188196 A048584 * A250194 A314293 A073895

Adjacent sequences: A085379 A085380 A085381 * A085383 A085384 A085385

Keyword

easy,nonn,changed

Author

Cino Hilliard, Aug 12 2003

Extensions

Offset 2 and a(2) from Michel Marcus, May 07 2024

Edited by Jon E. Schoenfield, May 07 2024

Status

approved