A085275 a(n) = Sum of n-th composite number and its largest prime divisor.

6, 9, 10, 12, 15, 15, 21, 20, 18, 21, 25, 28, 33, 27, 30, 39, 30, 35, 35, 34, 44, 51, 42, 39, 57, 52, 45, 49, 55, 50, 69, 51, 56, 55, 68, 65, 57, 66, 63, 76, 87, 65, 93, 70, 66, 78, 77, 85, 92, 77, 75, 111, 80, 95, 88, 91, 85, 84, 123, 91, 102, 129, 116, 99, 95, 104, 115, 124

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

For 91=7*13 we have 91+13 = 104; for 92=2*2*23 we have 92+23 = 115.

Mathematica

Total[#+FactorInteger[#][[-1, 1]]]&/@Select[Range[100], CompositeQ] (* Harvey P. Dale, Jul 05 2026 *)

Prog

(PARI) cminusp3(n) = { for(x=2, n, forstep(p=x, 2, -1, if(isprime(p) & x%p==0 & isprime(x)==0, print1(x+p, ", "); break); ) ) }

Crossrefs

Cf. A002808, A085271, A085273.

Sequence in context: A129492 A241913 A053869 * A177201 A090466 A090428

Adjacent sequences: A085272 A085273 A085274 * A085276 A085277 A085278

Keyword

easy,nonn,changed

Author

Cino Hilliard, Aug 12 2003

Extensions

Offset changed to 1 by Georg Fischer, May 12 2026

Status

approved