A097455 a(n) = gcd(prime(n)+1, composite(n)).

1, 4, 6, 8, 3, 2, 6, 2, 3, 2, 2, 2, 21, 22, 24, 1, 2, 1, 4, 6, 2, 1, 2, 5, 2, 2, 13, 4, 2, 2, 1, 2, 6, 7, 50, 1, 2, 2, 1, 2, 3, 2, 12, 2, 9, 8, 1, 2, 4, 23, 2, 24, 2, 3, 2, 11, 6, 16, 1, 2, 4, 1, 2, 3, 2, 6, 1, 2, 3, 2, 1, 24, 2, 11, 20, 6, 26, 1, 2, 2, 10, 1, 16, 2, 5, 4, 9, 2, 7, 8, 1, 2, 1, 4, 125

Offset

1,2

Links

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

Mathematica

Module[{nn=100, prs, cmps}, prs=Prime[Range[nn]]; cmps=Take[Complement[ Range[ Prime[nn]], prs], nn]; GCD@@@Thread[{prs+1, cmps}]] (* Harvey P. Dale, Sep 05 2013 *)

Prog

(PARI) primecompgcd(n) = { for(x=1, n, y=gcd(prime(x)+1, composite(x)); print1(y", ") ) } \ the n-th composite composite(n) = { local(c, x); c=1; x=0; while(c <= n, x++; if(!isprime(x), c++); ); return(x) }

Crossrefs

Cf. A000040, A002808.

Sequence in context: A217296 A330154 A179371 * A201520 A179022 A021685

Adjacent sequences: A097452 A097453 A097454 * A097456 A097457 A097458

Keyword

nonn

Author

Cino Hilliard, Aug 23 2004

Status

approved