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 A065567 T(n,m) is the sum over all m-subsets of {1,...,n} of the gcd of the subset. 2
 1, 3, 1, 6, 3, 1, 10, 7, 4, 1, 15, 11, 10, 5, 1, 21, 20, 21, 15, 6, 1, 28, 26, 36, 35, 21, 7, 1, 36, 38, 60, 71, 56, 28, 8, 1, 45, 50, 90, 127, 126, 84, 36, 9, 1, 55, 67, 132, 215, 253, 210, 120, 45, 10, 1, 66, 77, 177, 335, 463, 462, 330, 165, 55, 11, 1, 78, 105, 250, 512 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS First differences of row sums equals A034738. LINKS EXAMPLE Triangle begins:   1;   3,1;   6,3,1;   10,7,4,1;   15,11,10,5,1;   ... T(4,2)=7 since gcd(1,2) + gcd(1,3) + gcd(1,4) + gcd(2,3) + gcd(2,4) + gcd(3,4) = 7. MAPLE with(combstruct): a065567_row := proc(n) local k, L, l, R, comb; R := NULL; for k from 1 to n do    L := 0;    comb := iterstructs(Combination(n), size=k):    while not finished(comb) do       l := nextstruct(comb);       L := L + igcd(op(l));    od;    R := R, L; od; R end: # Peter Luschny, Dec 07 2010 MATHEMATICA Table[Plus@@(GCD@@@KSubsets[Range[n], m]), {n, 16}, {m, n}] CROSSREFS Cf. A065568, A034738. Sequence in context: A122432 A131110 A133093 * A100861 A131031 A130452 Adjacent sequences:  A065564 A065565 A065566 * A065568 A065569 A065570 KEYWORD nonn,tabl AUTHOR Wouter Meeussen, Nov 30 2001 STATUS approved

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Last modified August 9 21:08 EDT 2022. Contains 356026 sequences. (Running on oeis4.)