A325701 - OEIS

A325701

Nonprime Heinz numbers of integer partitions whose reciprocal factorial sum is the reciprocal of an integer.

1, 9, 25, 49, 77, 121, 125, 169, 221, 245, 289, 323, 343, 361, 375, 437, 529, 841, 899, 961, 1331, 1369, 1517, 1681, 1763, 1849, 1859, 2021, 2197, 2209, 2401, 2773, 2809, 2873, 3127, 3481, 3721, 3757, 4087, 4489, 4757, 4913, 5041, 5183, 5329, 5929, 6137, 6241

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OFFSET

1,2

COMMENTS

The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).

The reciprocal factorial sum of an integer partition (y_1,...,y_k) is 1/y_1! + ... + 1/y_k!.

LINKS

Table of n, a(n) for n=1..48.

EXAMPLE

The sequence of terms together with their prime indices begins:

1: {}

9: {2,2}

25: {3,3}

49: {4,4}

77: {4,5}

121: {5,5}

125: {3,3,3}

169: {6,6}

221: {6,7}

245: {3,4,4}

289: {7,7}

323: {7,8}

343: {4,4,4}

361: {8,8}

375: {2,3,3,3}

437: {8,9}

529: {9,9}

841: {10,10}

899: {10,11}

961: {11,11}

For example, the sequence contains 245 because the prime indices of 245 are {3,4,4}, with reciprocal sum 1/6 + 1/24 + 1/24 = 1/4.

MATHEMATICA

Select[Range[1000], !PrimeQ[#]&&IntegerQ[1/Total[Cases[FactorInteger[#], {p_, k_}:>k/PrimePi[p]!]]]&]

CROSSREFS

Factorial numbers: A000142, A007489, A022559, A064986, A108731, A115944, A284605, A325508, A325616.

Reciprocal factorial sum: A002966, A316854, A316857, A325618, A325620, A325622, A325623.

Sequence in context: A339727 A339128 A113659 * A113745 A348742 A016754

Adjacent sequences: A325698 A325699 A325700 * A325702 A325703 A325704

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 17 2019

STATUS

approved