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A304253
Numbers k such that k = Product (p_j^e_j) = Sum (prime(p_j)^e_j).
1
20, 68, 76, 92, 8248
OFFSET
1,1
COMMENTS
Fixed points of A304251.
EXAMPLE
68 is a term because 68 = 2^2*17 = prime(1)^2*prime(7) = prime(prime(1))^2 + prime(prime(7)).
8248 is a term because 8248 = 2^3*1031 = prime(1)^3*prime(173) = prime(prime(1))^3 + prime(prime(173)).
MATHEMATICA
a[n_] := Plus @@ (Prime[#[[1]]]^#[[2]] & /@ FactorInteger[n]); Select[Range[10000], a[#] == # &]
PROG
(PARI) isok(n) = my(f=factor(n)); n == sum(k=1, #f~, prime(f[k, 1])^f[k, 2]); \\ Michel Marcus, May 09 2018
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Ilya Gutkovskiy, May 09 2018
STATUS
approved