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A196527 Greatest common divisor of sums of first n prime numbers and first n composite numbers. 3
2, 5, 2, 1, 1, 1, 1, 1, 2, 1, 4, 1, 7, 1, 8, 1, 1, 1, 1, 1, 8, 7, 1, 1, 1, 3, 2, 1, 4, 3, 1, 1, 28, 1, 1, 1, 1, 1, 2, 1, 1, 3, 1, 1, 2, 1, 1, 1, 26, 1, 2, 1, 1, 1, 2, 1, 6, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 1, 1, 1, 10, 1, 2, 1, 1, 1, 1, 3, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) = gcd(A007504(n),A053767(n));

a(A196528(n)) = n and a(m) <> n for m < A196528(n).

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1) = gcd(2,4) = 2;

a(2) = gcd(2+3,4+6) = gcd(5,10) = 5;

a(3) = gcd(2+3+5,4+6+8) = gcd(10,18) = 2;

a(4) = gcd(2+3+5+7,4+6+8+9) = gcd(17,19) = 1.

MATHEMATICA

Module[{nn=90, pr, cmp}, pr=Accumulate[Prime[Range[nn]]]; cmp=Accumulate[ Take[Select[Range[2nn], CompositeQ], nn]]; GCD@@#&/@Thread[{pr, cmp}]] (* Harvey P. Dale, Jul 29 2017 *)

CROSSREFS

Cf. A196529.

Sequence in context: A193083 A146103 A245172 * A064334 A320032 A270061

Adjacent sequences:  A196524 A196525 A196526 * A196528 A196529 A196530

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 03 2011

STATUS

approved

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Last modified March 26 04:32 EDT 2019. Contains 321481 sequences. (Running on oeis4.)