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A049518 Starting index of a string of exactly 2 consecutive equal digits in the decimal expansion of Pi. 7
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 (list; graph; refs; listen; history; text; internal format)
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: A101066 A061442 A049514 * A133633 A038509 A067793

Adjacent sequences:  A049515 A049516 A049517 * A049519 A049520 A049521

KEYWORD

nonn,base

AUTHOR

Harvey P. Dale

STATUS

approved

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Last modified January 26 17:16 EST 2020. Contains 331280 sequences. (Running on oeis4.)