A079772 Let C(n) be the n-th composite number; then a(n) is the smallest number > C(n) and not coprime to C(n).

6, 8, 10, 12, 12, 14, 16, 18, 18, 20, 22, 24, 24, 26, 30, 28, 30, 30, 32, 34, 36, 36, 40, 38, 40, 42, 42, 44, 46, 48, 48, 50, 56, 52, 54, 54, 56, 60, 58, 60, 60, 62, 64, 66, 66, 70, 68, 70, 72, 72, 74, 76, 78, 78, 84, 80, 82, 84, 84, 86, 90, 88, 90, 90, 92, 98, 94, 96, 96, 100

Offset

1,1

Comments

a(n) = A002808(n) + A056608(n). - Vladeta Jovovic, Jan 31 2003

Links

Table of n, a(n) for n=1..70.

Formula

a(n) = C(n) + smallest prime divisor of C(n).

Example

C(4) = 9 and C(5) = 10 hence a(4) = a(5) = 12.
For 91=7*13 we have 91+7 = 98; for 92=2*2*23 we have 92-2 = 94

Prog

(PARI) cminusp31(n) = \sum c+min prime div { for(x=2, n, forprime(p=2, floor(sqrt(x)), if(x%p==0 & isprime(x)==0, print1(x+p, ", "); break); ) ) }

Crossrefs

Sequence in context: A171562 A018221 A071278 * A080731 A080257 A331201

Adjacent sequences: A079769 A079770 A079771 * A079773 A079774 A079775

Keyword

nonn

Author

Amarnath Murthy, Jan 31 2003

Extensions

More terms from Cino Hilliard, Aug 12 2003

Status

approved