A325621 - OEIS

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A325621

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

1, 2, 4, 8, 9, 16, 18, 32, 36, 64, 72, 81, 128, 144, 162, 256, 288, 324, 375, 512, 576, 648, 729, 750, 1024, 1152, 1296, 1458, 1500, 2048, 2304, 2592, 2916, 3000, 3375, 4096, 4608, 5184, 5832, 6000, 6561, 6750, 8192, 9216, 10368, 11664, 12000, 13122, 13500

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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..49.

EXAMPLE

The sequence of terms together with their prime indices begins:

1: {}

2: {1}

4: {1,1}

8: {1,1,1}

9: {2,2}

16: {1,1,1,1}

18: {1,2,2}

32: {1,1,1,1,1}

36: {1,1,2,2}

64: {1,1,1,1,1,1}

72: {1,1,1,2,2}

81: {2,2,2,2}

128: {1,1,1,1,1,1,1}

144: {1,1,1,1,2,2}

162: {1,2,2,2,2}

256: {1,1,1,1,1,1,1,1}

288: {1,1,1,1,1,2,2}

324: {1,1,2,2,2,2}

375: {2,3,3,3}

512: {1,1,1,1,1,1,1,1,1}

MATHEMATICA

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

CROSSREFS

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

Reciprocal factorial sum: A002966, A058360, A316856, A325619, A325620, A325623.

Sequence in context: A152111 A316856 A324524 * A025611 A049439 A251642

Adjacent sequences: A325618 A325619 A325620 * A325622 A325623 A325624

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 13 2019

STATUS

approved