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A119784
Numerator of Sum[Sum[(-1)^(i+1)*1/(i*j)^2, {i, 1, n}], {j, 1, n}].
0
1, 15, 1519, 23575, 15907111, 5224037, 13034567237, 206747823917, 51412399560631, 10224262569323, 152012226379719803, 151406414338463843, 4372018721271579430163, 4359099317599237566323, 21975413631947472215359
OFFSET
1,2
COMMENTS
Prime p divides a((p-1)/2) for p>3. p^2 divides a(p-1) for prime p>3.
FORMULA
a(n) = numerator[Sum[Sum[(-1)^(i+1)*1/(i*j)^2, {i, 1, n}], {j, 1, n}]]. a(n) = A119682(n)*A007406(n).
MATHEMATICA
Numerator[Table[Sum[Sum[(-1)^(i+1)*1/(i*j)^2, {i, 1, n}], {j, 1, n}], {n, 1, 20}]]
CROSSREFS
Sequence in context: A338634 A209680 A122469 * A199228 A344638 A209681
KEYWORD
frac,nonn
AUTHOR
Alexander Adamchuk, Jun 25 2006
STATUS
approved