cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A238744 Irregular table read by rows: T (n, k) gives the number of primes p such that p^k divides n; table omits all zero values.

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%I A238744 #13 May 15 2022 11:40:05
%S A238744 1,1,1,1,1,2,1,1,1,1,1,1,2,1,2,1,1,2,2,1,1,1,1,1,2,1,1,2,1,2,2,1,2,1,
%T A238744 1,1,1,2,1,1,1,2,1,1,3,1,1,1,1,1,1,2,2,2,2,2,1,2,2,2,1,1,1,3,1,2,1,2,
%U A238744 1,2,1,2,1,1,1,1,1,2,1,2,2,1,1,2,1,1,2
%N A238744 Irregular table read by rows: T (n, k) gives the number of primes p such that p^k divides n; table omits all zero values.
%C A238744 If the prime signature of n (nonincreasing version) is viewed as a partition, row n gives the conjugate partition.
%F A238744 Row n is identical to row A124859(n) of table A212171.
%e A238744 24 = 2^3*3 is divisible by two prime numbers (2 and 3), one square of a prime (4 = 2^2), and one cube of a prime (8 = 2^3); therefore, row 24 of the table is {2,1,1}.
%e A238744 From _Gus Wiseman_, Mar 31 2022: (Start)
%e A238744 Rows begin:
%e A238744      1: ()        16: (1,1,1,1)    31: (1)
%e A238744      2: (1)       17: (1)          32: (1,1,1,1,1)
%e A238744      3: (1)       18: (2,1)        33: (2)
%e A238744      4: (1,1)     19: (1)          34: (2)
%e A238744      5: (1)       20: (2,1)        35: (2)
%e A238744      6: (2)       21: (2)          36: (2,2)
%e A238744      7: (1)       22: (2)          37: (1)
%e A238744      8: (1,1,1)   23: (1)          38: (2)
%e A238744      9: (1,1)     24: (2,1,1)      39: (2)
%e A238744     10: (2)       25: (1,1)        40: (2,1,1)
%e A238744     11: (1)       26: (2)          41: (1)
%e A238744     12: (2,1)     27: (1,1,1)      42: (3)
%e A238744     13: (1)       28: (2,1)        43: (1)
%e A238744     14: (2)       29: (1)          44: (2,1)
%e A238744     15: (2)       30: (3)          45: (2,1)
%e A238744 (End)
%t A238744 Table[Length/@Table[Select[Last/@FactorInteger[n],#>=k&],{k,Max@@Last/@FactorInteger[n]}],{n,2,100}] (* _Gus Wiseman_, Mar 31 2022 *)
%Y A238744 Row lengths are A051903(n); row sums are A001222(n).
%Y A238744 Cf. A217171.
%Y A238744 These partitions are ranked by A238745.
%Y A238744 For prime indices A296150 instead of exponents we get A321649, rev A321650.
%Y A238744 A000700 counts self-conjugate partitions, ranked by A088902.
%Y A238744 A003963 gives product of prime indices, conjugate A329382.
%Y A238744 A008480 gives number of permutations of prime indices, conjugate A321648.
%Y A238744 A056239 adds up prime indices, row sums of A112798.
%Y A238744 A124010 gives prime signature, sorted A118914, length A001221.
%Y A238744 A352486-A352490 are sets related to the fixed points of A122111.
%Y A238744 Cf. A000701, A000720, A046682, A238747, A258116, A319005, A330644, A352491.
%K A238744 nonn,tabf
%O A238744 2,6
%A A238744 _Matthew Vandermast_, Apr 28 2014