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A231230 Numbers n such that, in the prime factorization of n, the sum of the primes equals the squared sum of exponents. 0
28, 98, 132, 198, 351, 368, 726, 1092, 1375, 1488, 1521, 1540, 1638, 2232, 2295, 2320, 3008, 3025, 3348, 3822, 3825, 3850, 4048, 4232, 5022, 5390, 5800, 6375, 6591, 6655, 7098, 7980, 8470, 11328, 11375, 11970, 12012, 12432, 13005, 14500, 15925, 16992, 18018 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
98 = 7^2 * 2, sum of primes is 9, sum of exponents is 3, so 98 is in the sequence.
MATHEMATICA
t = {}; n = 1; While[Length[t] < 50, n++; {p, e} = Transpose[FactorInteger[n]]; If[Total[p] == Total[e]^2, AppendTo[t, n]]]; t (* T. D. Noe, Nov 08 2013 *)
PROG
(PARI) isok(n) = {f = factor(n); sum(i=1, #f~, f[i, 1]) == sum(i=1, #f~, f[i, 2])^2; } \\ Michel Marcus, Nov 07 2013
CROSSREFS
Sequence in context: A130085 A211495 A233374 * A233375 A219691 A212777
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Nov 05 2013
STATUS
approved

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Last modified March 29 05:43 EDT 2024. Contains 371264 sequences. (Running on oeis4.)