A101754 Numbers n such that the sum of the first n decimal places of Catalan's constant is prime.
9, 11, 14, 22, 23, 25, 31, 32, 39, 45, 46, 55, 56, 57, 63, 64, 68, 73, 78, 81, 84, 90, 94, 112, 115, 117, 162, 163, 169, 172, 179, 184, 200, 208, 212, 221, 227, 233, 240, 253, 270, 272, 283, 290, 303, 327, 329, 339, 345, 347, 348, 365, 378, 381, 396, 398, 409
Offset: 1
Examples
The sums of the first n decimal places of Catalan's constant are listed in A099616: 9, 10, 15, 24, 30, 35, 40, 49, 53, 54, 61, ... Of these, the first one that is prime is 53 which is the 9th term. The first term in our sequence is therefore 9. The partial sum 61 is also prime and this appears in the 11th place, so the second term of our sequence is 11.
Crossrefs
Cf. A099616.
Programs
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Mathematica
Flatten[Position[Accumulate[RealDigits[N[Catalan,500]][[1]]], ?PrimeQ]] (* _Harvey P. Dale, May 10 2011 *)