A045856 Numbers whose square has initial digit '2'.

5, 15, 16, 17, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 448, 449, 450, 451, 452, 453, 454, 455, 456

Offset

1,1

Links

Seiichi Manyama, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[500], IntegerDigits[#^2][[1]]==2&] (* Harvey P. Dale, Apr 15 2024 *)

Prog

(PARI) isok(n) = digits(n^2)[1] == 2; \\ Michel Marcus, May 28 2017

Crossrefs

Cf. A045785

Sequence in context: A184288 A015666 A291627 * A102185 A030486 A101238

Adjacent sequences: A045853 A045854 A045855 * A045857 A045858 A045859

Keyword

nonn,base

Author

Jeff Burch

Extensions

Corrected by Seiichi Manyama, May 28 2017

Status

approved