A058938 Numbers k such that the sum of the first k digits of the decimal expansion of Pi is prime.

1, 6, 8, 13, 20, 21, 34, 36, 48, 56, 63, 87, 89, 92, 94, 104, 106, 107, 111, 116, 117, 118, 120, 130, 132, 133, 141, 146, 147, 162, 170, 173, 179, 183, 185, 186, 198, 202, 203, 206, 215, 217, 219, 220, 225, 242, 248, 249, 258, 264, 265, 270, 271, 285, 290, 291

Offset

1,2

Links

Table of n, a(n) for n=1..56.

Example

6 is a term because 3 + 1 + 4 + 1 + 5 + 9 = 23, which is prime.

Maple

Digits := 2000: it := evalf(Pi, 2000): for i from 1 to 2000 do a[i] := floor(it): it := 10*(it-floor(it)): od: s := 0: for i from 1 to 2000 do s := s+a[i]: if isprime(s) then printf(`%d, `, i) fi: od:

Mathematica

a = First[ RealDigits[ N[ Pi, 300]]]; Do[ If[ PrimeQ[Plus @@ Take[a, n]], Print[n]], {n, 1, 300}]
Flatten[Position[Accumulate[RealDigits[\[Pi], 10, 500][[1]]], _?PrimeQ]]  (* Harvey P. Dale, Apr 03 2011 *)

Crossrefs

Cf. A000796, A071117, A133213.

Sequence in context: A190558 A063188 A373663 * A315877 A315878 A101729

Adjacent sequences: A058935 A058936 A058937 * A058939 A058940 A058941

Keyword

easy,nonn,base

Author

G. L. Honaker, Jr., Jan 11 2001

Extensions

More terms from James Sellers, Jan 14 2001

Status

approved