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A096527 Number of permutations of divisors of n such that all sums of triple adjacent divisors are primes. 3
0, 0, 0, 6, 0, 0, 0, 12, 6, 4, 0, 12, 0, 4, 4, 4, 0, 0, 0, 16, 12, 0, 0, 20, 6, 4, 12, 20, 0, 0, 0, 0, 4, 4, 24, 48, 0, 4, 12, 50, 0, 0, 0, 4, 12, 0, 0, 0, 0, 0, 0, 16, 0, 0, 24, 136, 12, 4, 0, 286, 0, 0, 96, 0, 24, 0, 0, 30, 0, 0, 0, 0, 0, 0, 32, 16, 4, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

a(A096530(n)) = 0, a(A096529(n)) > 0.

For square of terms of A053182(n), a(n) = 6. - Michel Marcus, May 08 2014

LINKS

Table of n, a(n) for n=1..79.

EXAMPLE

Divisors of n=10 are {1,2,5,10}:

[1,2,10,5]->(1+2+10,2+5+10)=(13,17), [1,10,2,5]->(1+10+2,10+2+5)=(13,17)

[5,2,10,1]->(5+2+10,2+10+1)=(17,13) and

[5,10,2,1]->(5+10+2,10+2+1)=(17,13): therefore a(10)=4.

PROG

(PARI) isokperm(v, nbd, d) = {for (j=1, nbd-2, if (! isprime(d[v[j]] + d[v[j+1]] + d[v[j+2]]), return (0)); ); return (1); }

a(n) = {d = divisors(n); nbd = #d; if (nbd > 2, sum(i=1, nbd!, isokperm(numtoperm(nbd, i), nbd, d))); } \\ Michel Marcus, May 03 2014

CROSSREFS

Cf. A096528, A000005.

Sequence in context: A028704 A028607 A308091 * A028599 A270850 A305324

Adjacent sequences:  A096524 A096525 A096526 * A096528 A096529 A096530

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jun 23 2004

EXTENSIONS

More terms from Michel Marcus, May 03 2014

STATUS

approved

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Last modified January 26 14:08 EST 2020. Contains 331280 sequences. (Running on oeis4.)