The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A049518 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A049518

Starting index of a string of exactly 2 consecutive equal digits in the decimal expansion of Pi.
(history; published version)

#10 by Susanna Cuyler at Fri Oct 18 21:33:20 EDT 2019

STATUS

proposed

approved

#9 by M. F. Hasler at Fri Oct 18 19:42:55 EDT 2019

STATUS

editing

proposed

#8 by M. F. Hasler at Fri Oct 18 19:42:19 EDT 2019

PROG

(PARI) A049518_upto(N=999)={default(realprecision, N); my(p=digits(precision(Pi, N=999)\10^-N)); forselect(i=1, #p-2, >p[i]==p[i+1] && p[i]!=p[i-1] && p[i]!=p[i+2]&&print1(i", "), [9..N-2]) } \\ M. F. Hasler, Oct 18 2019

#7 by M. F. Hasler at Fri Oct 18 19:01:25 EDT 2019

NAME

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

COMMENTS

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

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)

PROG

(PARI) p=digits(precision(Pi, N=999)\10^-N); for(i=1, #p-2, p[i]==p[i+1]&&p[i]!=p[i-1]&&p[i]!=p[i+2]&&print1(i", ")) \\ M. F. Hasler, Oct 18 2019

STATUS

approved

editing

#6 by Harvey P. Dale at Sat Jul 08 19:26:48 EDT 2017

STATUS

editing

approved

#5 by Harvey P. Dale at Sat Jul 08 19:26:44 EDT 2017

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 *)

STATUS

approved

editing

#4 by Russ Cox at Sat Mar 31 14:45:08 EDT 2012

AUTHOR

Harvey P. Dale (hpd1(AT)is2.nyu.edu)

Harvey P. Dale

Discussion

Sat Mar 31

14:45

OEIS Server: https://oeis.org/edit/global/965

#3 by N. J. A. Sloane at Fri Jan 09 03:00:00 EST 2009

KEYWORD

nonn,newbase

#2 by N. J. A. Sloane at Fri May 16 03:00:00 EDT 2003

KEYWORD

nonn,new

nonn

AUTHOR

Harvey P. Dale (hpd1@(AT)is2.nyu.edu)

#1 by N. J. A. Sloane at Sat Dec 11 03:00:00 EST 1999

NAME

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

DATA

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,...

CROSSREFS

Cf. A049514-A049523.

KEYWORD

nonn

AUTHOR

Harvey P. Dale (hpd1@is2.nyu.edu)

STATUS

approved