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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
OFFSET
1,1
COMMENTS
a(n) = gcd(A007504(n),A053767(n));
a(A196528(n)) = n and a(m) <> n for m < A196528(n).
LINKS
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: A146103 A245172 A371751 * A064334 A320032 A270061
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Oct 03 2011
STATUS
approved