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A307386
Heinz numbers of integer partitions with Durfee square of length 3.
4
125, 175, 245, 250, 275, 325, 343, 350, 375, 385, 425, 455, 475, 490, 500, 525, 539, 550, 575, 595, 605, 625, 637, 650, 665, 686, 700, 715, 725, 735, 750, 770, 775, 805, 825, 833, 845, 847, 850, 875, 910, 925, 931, 935, 950, 975, 980, 1000, 1001, 1015, 1025
OFFSET
1,1
COMMENTS
The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).
The Durfee square of an integer partition is the largest square contained in its Young diagram.
EXAMPLE
The sequence of terms together with their prime indices begins:
125: {3,3,3}
175: {3,3,4}
245: {3,4,4}
250: {1,3,3,3}
275: {3,3,5}
325: {3,3,6}
343: {4,4,4}
350: {1,3,3,4}
375: {2,3,3,3}
385: {3,4,5}
425: {3,3,7}
455: {3,4,6}
475: {3,3,8}
490: {1,3,4,4}
500: {1,1,3,3,3}
525: {2,3,3,4}
539: {4,4,5}
550: {1,3,3,5}
575: {3,3,9}
595: {3,4,7}
MATHEMATICA
durf[n_]:=Length[Select[Range[PrimeOmega[n]], Reverse[Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]][[#]]>=#&]];
Select[Range[100], durf[#]==3&]
CROSSREFS
Positions of 3 in A257990. The Durfee length 1 case is A093641. The Durfee length 2 case is A325164. The enumeration of Durfee length 2 partitions by sum is given by A006918, while that of Durfee length 3 partitions is given by A117485.
Sequence in context: A202240 A069656 A196943 * A307515 A038513 A251125
KEYWORD
nonn
AUTHOR
Gus Wiseman, Apr 06 2019
STATUS
approved