The On-Line Encyclopedia of Integer Sequences (OEIS)

A049304 revision #23

A049304

Numbers k such that k is a substring of 6^k.

6, 7, 9, 13, 21, 22, 23, 29, 39, 40, 42, 44, 45, 48, 53, 55, 56, 60, 63, 64, 65, 67, 68, 69, 70, 73, 74, 75, 76, 77, 79, 82, 83, 87, 89, 92, 93, 94, 98, 105, 107, 127, 129, 131, 134, 137, 143, 147, 152, 163, 165, 167, 174, 179, 184, 189, 197, 224, 226, 227, 234, 240

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

David A. Corneth, Table of n, a(n) for n = 1..10000

EXAMPLE

9 is in the sequence because 6^9 = 10077696 contains 9 as a substring. - David A. Corneth, Aug 13 2021

MATHEMATICA

Select[Range[250], SequenceCount[IntegerDigits[6^#], IntegerDigits[#]]>0&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 03 2018 *)

PROG

(Python)

def ok(n): return str(n) in str(6**n)

print(list(filter(ok, range(241)))) # Michael S. Branicky, Aug 13 2021

(PARI) is(n) = { my(digs6n, digsn, streak, i, j); digs6n = digits(6^n); digsn = digits(n); for(i = 1, #digs6n + 1 - #digsn, streak = 0; for(j = 1, #digsn, if(digs6n[i + j - 1] == digsn[j], streak++ , next(2) ) ); if(streak == #digsn, return(1) ) ); 0 } \\ David A. Corneth, Aug 13 2021

CROSSREFS

Cf. A000400, A032740, A049301-A049307.

Sequence in context: A048585 A169761 A376243 * A168614 A045014 A047591

Adjacent sequences: A049301 A049302 A049303 * A049305 A049306 A049307

KEYWORD

nonn,base,easy

AUTHOR

David W. Wilson

STATUS

editing