A239210 Numbers k such that k^2 is not divisible by any of its nonzero digits.

7, 17, 23, 26, 47, 53, 67, 73, 76, 77, 83, 86, 94, 97, 143, 157, 163, 167, 173, 176, 187, 193, 194, 197, 223, 233, 236, 244, 253, 256, 257, 260, 274, 277, 283, 287, 293, 307, 313, 314, 457, 473, 493, 503, 517, 523, 527, 533, 547, 553, 577, 583, 587, 607, 613

Offset

1,1

Links

Colin Barker, Table of n, a(n) for n = 1..1000

Example

53 is a term because 53^2 = 2809 is not divisible by 2, 8 or 9.

Mathematica

ndnzQ[n_]:=Count[n^2/Select[IntegerDigits[n^2], #!=0&], _?IntegerQ]==0; Select[Range[750], ndnzQ] (* Harvey P. Dale, Jun 02 2015 *)

Prog

(PARI) isOK(n) = my(v=vecsort(digits(n^2), , 8)); for(i=1+(v[1]==0), #v, if(n^2%v[i]==0, return(0))); 1
s=[]; for(n=1, 1000, if(isOK(n), s=concat(s, n))); s
(Python)
def ok(n): return not any(n*n%int(d) == 0 for d in str(n*n) if d != '0')
print(list(filter(ok, range(1, 614)))) # Michael S. Branicky, Jul 17 2021

Crossrefs

Cf. A239211, A239212, A239213.

Sequence in context: A087168 A247560 A215824 * A191087 A032454 A107643

Adjacent sequences: A239207 A239208 A239209 * A239211 A239212 A239213

Keyword

nonn,base

Author

Colin Barker, Mar 12 2014

Status

approved