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Search: id:A134449
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| A134449 |
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Sum of even products less sum of odd products of different pairs of numbers from 1 to n. |
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+0
1
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| 0, 2, 5, 29, 39, 129, 150, 374, 410, 860, 915, 1707, 1785, 3059, 3164, 5084, 5220, 7974, 8145, 11945, 12155, 17237, 17490, 24114, 24414, 32864, 33215, 43799, 44205, 57255, 57720, 73592, 74120, 93194, 93789, 116469, 117135, 143849, 144590, 175790
(list; graph; listen)
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OFFSET
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0,2
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EXAMPLE
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{1,2,3} -> 1*2-1*3+2*3 = 5
{1,2,3,4} -> 1*2-1*3+1*4+2*3+2*4+3*4 = 29
{1,2,3,4,5} -> 1*2-1*3+1*4-1*5+2*3+2*4+2*5+3*4-3*5+4*5 = 39
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MAPLE
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P:=proc(n) local a, i, j, k, w; for i from 1 by 1 to n do a:=0; for j from 1 by 1 to i do w:=j; k:=i; while k>w do a:=a+w*k*(-1)^(w*k); k:=k-1; od; od; print(a); od; end: P(100);
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CROSSREFS
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Cf. A000914, A000915.
Sequence in context: A000472 A049050 A098858 this_sequence A103579 A061351 A126107
Adjacent sequences: A134446 A134447 A134448 this_sequence A134450 A134451 A134452
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KEYWORD
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easy,nonn
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AUTHOR
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Paolo P. Lava & Giorgio Balzarotti (ppl(AT)spl.at), Jan 31 2008
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