

A073110


Number of permutations p of (1,2,3,...,n) such that sigma(1+p(1))+sigma(2+p(2))+...+sigma(n+p(n))=2*n^2.


0



0, 1, 0, 2, 10, 37, 121, 725, 5160, 31794, 279136, 2137531, 21305316, 213311303, 2457648287, 30357607661, 387013387043, 5245097770693
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OFFSET

1,4


COMMENTS

It seems that for any permutation p of (1,2,3,...,n) for n>3, the equation: sigma(1+p(1))+sigma(2+p(2))+...+sigma(n+p(n))=m*n^2 has solutions for m=2 only.


LINKS

Table of n, a(n) for n=1..18.


PROG

(PARI) a(n)=sum(k=1, n!, if(sum(i=1, n, sigma(i+component(numtoperm(n, k), i)))2*n^2, 0, 1))


CROSSREFS

Sequence in context: A236767 A154323 A191349 * A034547 A246604 A124646
Adjacent sequences: A073107 A073108 A073109 * A073111 A073112 A073113


KEYWORD

nonn


AUTHOR

Benoit Cloitre, Aug 19 2002


EXTENSIONS

2 more terms from Ryan Propper, Aug 27 2005
a(12)a(18) from Robert Gerbicz, Nov 21 2010


STATUS

approved



