A342805 a(n) = (1/n)*(product of the terms of the n-th row of A177028).

1, 1, 1, 3, 1, 1, 4, 3, 1, 5, 1, 1, 18, 4, 1, 7, 1, 1, 24, 5, 1, 9, 4, 1, 10, 18, 1, 11, 1, 1, 12, 7, 5, 156, 1, 1, 14, 8, 1, 15, 1, 1, 288, 9, 1, 17, 4, 1, 90, 10, 1, 19, 21, 1, 20, 11, 1, 21, 1, 1, 22, 48, 8, 414, 1, 1, 24, 65, 1, 25, 1, 1, 234, 14, 1, 81, 1, 1, 784, 15

Offset

3,4

Links

Michel Marcus, Table of n, a(n) for n = 3..10000

Formula

For m in A090466, a(m) > 1.

For m in A090467, a(m) = 1.

Example

For n=3, A177028 row is (3), so a(3) = 3/3 = 1.
For n=6, A177028 row is (6, 3), so a(6) = 6*3/6 = 3.
For n=15, A177028 row is (15, 6, 3), so a(15) = 15*6*3/15 = 18.

Prog

(PARI) row(n)=my(v=List()); fordiv(2*n, k, if(k<2, next); if(k==n, break); my(s=(2*n/k-4+2*k)/(k-1)); if(denominator(s)==1, listput(v, s))); Vec(v); \\ A177028
a(n) = vecprod(row(n))/n;

Crossrefs

Cf. A090466, A090467, A177028, A342772.

Sequence in context: A125181 A157076 A348608 * A363901 A049999 A126015

Adjacent sequences: A342802 A342803 A342804 * A342806 A342807 A342808

Keyword

nonn

Author

Michel Marcus, Mar 22 2021

Status

approved