The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A239210 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A239210

Numbers k such that k^2 is not divisible by any of its nonzero digits.
(history; published version)

#16 by Michel Marcus at Sat Jul 17 02:50:25 EDT 2021

STATUS

reviewed

approved

#15 by Joerg Arndt at Sat Jul 17 02:23:27 EDT 2021

STATUS

proposed

reviewed

#14 by Michel Marcus at Sat Jul 17 00:25:56 EDT 2021

STATUS

editing

proposed

#13 by Michel Marcus at Sat Jul 17 00:25:43 EDT 2021

NAME

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

STATUS

proposed

editing

#12 by Michael S. Branicky at Sat Jul 17 00:24:35 EDT 2021

STATUS

editing

proposed

#11 by Michael S. Branicky at Sat Jul 17 00:24:19 EDT 2021

EXAMPLE

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

PROG

(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

STATUS

approved

editing

#10 by Harvey P. Dale at Tue Jun 02 17:00:39 EDT 2015

STATUS

editing

approved

#9 by Harvey P. Dale at Tue Jun 02 17:00:33 EDT 2015

MATHEMATICA

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

STATUS

approved

editing

#8 by Bruno Berselli at Thu Oct 30 07:32:43 EDT 2014

STATUS

proposed

approved

#7 by Colin Barker at Thu Oct 30 06:59:43 EDT 2014

STATUS

editing

proposed