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A085378
Difference between primes p and the largest prime divisor of p-1.
1
3, 4, 6, 10, 15, 16, 12, 22, 26, 34, 36, 36, 24, 40, 30, 56, 56, 64, 70, 66, 42, 78, 94, 96, 86, 54, 106, 106, 120, 118, 120, 116, 112, 146, 144, 160, 84, 130, 90, 176, 172, 190, 190, 188, 204, 186, 114, 210, 204, 222, 236, 246, 255, 132, 202, 266, 254, 274, 236
OFFSET
3,1
COMMENTS
This sequence contains only one prime number, the 3.
EXAMPLE
For prime 107 we have 107 - 53 = 54.
MAPLE
A085378 := proc(n)
ithprime(n)-A023503(n) ;
end proc:
seq( A085378(n), n=3..80) ; # R. J. Mathar, Sep 07 2016
MATHEMATICA
#-FactorInteger[#-1][[-1, 1]]&/@Prime[Range[3, 70]] (* Harvey P. Dale, Jan 04 2012 *)
PROG
(PARI) cminuspm1(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); ) ) }
CROSSREFS
Sequence in context: A167410 A302340 A310003 * A255879 A171096 A125869
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Aug 12 2003
STATUS
approved