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 A127481 Triangle T(n,k) read by rows: T(n,k) = sum_{l=k..n, l|n, k|l} l*phi(k). 2
 1, 3, 2, 4, 0, 6, 7, 6, 0, 8, 6, 0, 0, 0, 20, 12, 8, 18, 0, 0, 12, 8, 0, 0, 0, 0, 0, 42, 15, 14, 0, 24, 0, 0, 0, 32, 13, 0, 24, 0, 0, 0, 0, 0, 54, 18, 12, 0, 0, 60, 0, 0, 0, 0, 40, 12, 0, 0, 0, 0, 0, 0, 0, 0, 0, 110, 28, 24, 42, 32, 0, 36, 0, 0, 0, 0, 0, 48, 14, 0, 0, 0, 0, 0, 0, 0, 0 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA T(n,1) = A000203(n). T(n,n) = A002618(n). T(n,k) =sum_{l=k..n} A127093(n,l) * A054522(l,k), the matrix product of the infinite lower triangular matrices. EXAMPLE First few rows of the triangle are: 1; 3, 2; 4, 0, 6; 7, 6, 0, 8; 6, 0, 0, 0, 20, 12, 8, 18, 0, 0, 12; 8, 0, 0, 0, 0, 0, 42; 15, 14, 0, 24, 0, 0, 0, 32; ... MAPLE A127481 := proc(n, k)     a :=0 ;     for l from k to n do         if modp(n, l) =0 and modp(l, k) =0 then             a := a+l*numtheory[phi](k) ;         end if;     end do:     a ; end proc: # R. J. Mathar, Sep 06 2013 CROSSREFS Cf. A054522, A127093, A001157 (row sums), A002618, A127466. Sequence in context: A129237 A127099 A004545 * A284552 A328564 A154879 Adjacent sequences:  A127478 A127479 A127480 * A127482 A127483 A127484 KEYWORD nonn,tabl,easy AUTHOR Gary W. Adamson, Jan 15 2007 STATUS approved

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Last modified May 26 17:16 EDT 2020. Contains 334630 sequences. (Running on oeis4.)