A067757 Numbers k whose last digit is the k-th digit of sqrt(2).

15, 18, 20, 21, 39, 45, 47, 49, 67, 87, 92, 117, 122, 126, 147, 149, 162, 165, 170, 179, 192, 197, 205, 235, 237, 264, 272, 274, 275, 279, 282, 286, 289, 292, 297, 305, 313, 318, 335, 340, 344, 345, 356, 381, 384, 394, 403, 409, 418, 433, 446, 449, 471, 476

Offset

1,1

Comments

The k-th digit of sqrt(2) is calculated starting after the decimal point. - Harvey P. Dale, Jan 29 2023

Links

Chai Wah Wu, Table of n, a(n) for n = 1..10000

Example

Let d(n) be the n-th digit of sqrt(2)=1.4142... so d(1)=4, d(2)=1 etc. d(122)=2 and 2 is the last digit of 122 hence 122 is in the sequence.

Mathematica

Module[{nn=500, sq2}, sq2=RealDigits[Sqrt[2], 10, nn][[1]]; Select[Range[nn-1], Mod[ #, 10] == sq2[[#+1]]&]] (* Harvey P. Dale, Jan 29 2023 *)

Prog

(Python 3.8+)
from math import isqrt
A067757_list = [i for i, d in enumerate(str(isqrt(2*100**100000))) if i % 10 == int(d)] # Chai Wah Wu, Jul 08 2021

Crossrefs

Cf. A002193, A067750, A067789.

Sequence in context: A159840 A124609 A102500 * A063779 A125006 A125008

Adjacent sequences: A067754 A067755 A067756 * A067758 A067759 A067760

Keyword

easy,nonn,base

Author

Benoit Cloitre, Mar 07 2002

Status

approved