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A085273

Difference between n-th composite number and its largest prime divisor.

2, 3, 6, 6, 5, 9, 7, 10, 14, 15, 15, 14, 11, 21, 20, 13, 24, 21, 25, 30, 22, 17, 28, 33, 19, 26, 35, 35, 33, 40, 23, 45, 42, 45, 34, 39, 51, 44, 49, 38, 29, 55, 31, 56, 62, 52, 55, 51, 46, 63, 69, 37, 70, 57, 66, 65, 75, 78, 41, 77, 68, 43, 58, 77, 85, 78, 69, 62, 47, 76, 93, 91

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10000

EXAMPLE

For 91=7*13 we have 91-13 = 78.

For 92=2*2*23 we have 92-23 = 69.

MATHEMATICA

DeleteCases[Table[n - FactorInteger[n][[-1, 1]], {n, 100}], 0 _] (* Ivan Neretin, Jun 20 2019 *)

PROG

(PARI) cminusp2(n) = { for(x=2, n, forstep(p=x, 2, -1, if(isprime(p) & x%p==0 & isprime(x)==0, print1(x-p, ", "); break); ) ) }