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A074213
Sum of the prime factors of k equals half the sum of the prime factors of k + 1.
0
90, 208, 867, 1161, 1674, 2139, 2295, 2821, 3683, 9675, 10374, 11357, 14823, 17685, 20436, 23750, 23895, 28035, 39039, 39962, 43687, 43813, 47564, 63624, 75615, 79281, 97382, 100855, 103246, 119350, 124749, 126575, 136344, 157250, 178503, 201877, 218368, 220375
OFFSET
1,1
EXAMPLE
The sum of the prime factors of 90 = 2 * 3^2 * 5 is 2 + 3 + 5 = 10; the sum of the prime factors of 91 = 7 * 13 = 20. Hence 90 belongs to the sequence.
MATHEMATICA
p[n_] := Apply[Plus, Transpose[FactorInteger[n]][[1]]]; Select[Range[2, 10^5], 2*p[ # ] == p[ # + 1] &]
PROG
(PARI) is(k) = 2*vecsum(factor(k)[, 1]) == vecsum(factor(k+1)[, 1]); \\ Jinyuan Wang, Jan 15 2022
CROSSREFS
Cf. A008472.
Sequence in context: A044422 A044803 A235081 * A231961 A237131 A363729
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Oct 18 2002
EXTENSIONS
Offset changed to 1 and more terms from Jinyuan Wang, Jan 15 2022
STATUS
approved