A049518 Starting index of a string of exactly 2 consecutive equal digits in the decimal expansion of Pi.

25, 35, 45, 60, 80, 95, 118, 126, 131, 136, 175, 183, 186, 202, 205, 212, 216, 218, 231, 258, 277, 283, 308, 310, 316, 318, 323, 361, 363, 365, 373, 378, 396, 402, 428, 438, 446, 454, 460, 473, 485, 495, 504, 508, 512, 517, 536, 560, 593, 622

Offset

0,1

Comments

Digits 3,1,4,... are indexed 1,2,3,...

See A049514 for the variant "at least 2", which differs from a(11) on. - M. F. Hasler, Oct 18 2019

Links

Table of n, a(n) for n=0..49.

Example

From M. F. Hasler, Oct 18 2019: (Start)
The integer part of Pi*10^22 ends in 33, i.e., at position 22 starts the (first) string of two repeated digits 3, therefore a(1) = 22.
At position 154 starts a string of three '1's, so sequence A049514 lists both, 154 and 155, but this sequence lists none of these. (End)

Mathematica

Flatten[Position[Partition[RealDigits[Pi, 10, 1000][[1]], 4, 1], _?(#[[1]] != #[[2]] && #[[2]]==#[[3]]&&#[[3]]!=#[[4]]&), 1, Heads->False]]+1 (* Harvey P. Dale, Jul 08 2017 *)

Prog

(PARI) A049518_upto(N=999)={default(realprecision, N); my(p=digits(Pi\10^-N)); select(i->p[i]==p[i+1] && p[i]!=p[i-1] && p[i]!=p[i+2], [9..N-2])} \\ M. F. Hasler, Oct 18 2019

Crossrefs

Cf. A049514-A049523.

Sequence in context: A340121 A061442 A049514 * A334146 A133633 A038509

Adjacent sequences: A049515 A049516 A049517 * A049519 A049520 A049521

Keyword

nonn,base

Author

Harvey P. Dale

Status

approved