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A205881
Second pentagonal numbers that are interprime.
1
15, 26, 260, 495, 610, 950, 1190, 1962, 2420, 2667, 3197, 3337, 3480, 6370, 7597, 14455, 15965, 18205, 39447, 42926, 43947, 50325, 57135, 63140, 64377, 65000, 66255, 74037, 78090, 82251, 86520, 87967, 106267, 107870, 121980, 125426, 136957, 140607, 153760
OFFSET
1,1
COMMENTS
Intersection of A005449 and A024675. Also see references in A075190 about interprimes of different forms.
EXAMPLE
a(1) = 15 = A024675(5) = A005449(3).
a(2) = 26 = A024675(8) = A005449(4).
MATHEMATICA
Select[Mean/@Partition[Prime[Range[15000]], 2, 1], IntegerQ[(Sqrt[1+24#]-1)/6]&] (* Harvey P. Dale, Feb 02 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Feb 01 2012
STATUS
approved