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Search: id:A123617
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| 1, 2, 10, 68, 618, 6352, 71188, 841332, 10352618, 131328068, 1706742160, 22619741212, 304685855700, 4160480013848, 57476485976388, 802048167035968, 11290551106506218, 160168176177137896, 2287724464324213972
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OFFSET
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0,2
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COMMENT
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Related sequences: A123610(2n+1,n) = A000891(n); A123610(2n+2,n) = A123618(n); A123610(2n+2,n)/(n+1) = A123619(n).
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PROGRAM
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(PARI) {a(n)=if(n==0, 1, (1/2/n)*sumdiv(2*n, d, if(gcd(n, d)==d, eulerphi(d)*binomial(2*n/d, n/d)^2, 0)))}
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CROSSREFS
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Cf. A123610 (triangle); A000891, A123618.
Adjacent sequences: A123614 A123615 A123616 this_sequence A123618 A123619 A123620
Sequence in context: A136658 A104098 A056755 this_sequence A139715 A051575 A121201
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Oct 03 2006
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