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A277079 Least number k for which k^n contains n as a substring and n^k contains k as a substring. 1
1, 35, 7, 61, 5, 6, 3, 7, 5, 10, 11, 15, 6, 36, 7, 16, 17, 33, 16, 44, 6, 48, 36, 3, 5, 9, 31, 8, 32, 69, 8, 5, 8, 5, 2, 2, 9, 8, 6, 6, 5, 8, 7, 6, 6, 9, 8, 6, 2, 7, 2, 8, 6, 5, 5, 5, 3, 8, 9, 6, 4, 3, 6, 6, 6, 25, 5, 6, 3, 6, 3, 3, 2, 6, 5, 6, 3, 7, 8, 7, 4, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = n for 1, 5, 6, 10, 11, 16, 17.

Records for a(1) = 1, a(2) = 35, a(4) = 61, a(30) = 69, a(1061) = 84, a(1256) = 91, ...

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..1000

EXAMPLE

2^35 = 34359738368 and 35 is a substring;

35^2 = 1225 and 2 is a substring.

MAPLE

P:=proc(q) local a, b, j, k, n, ok; for n from 1 to q do a:=convert(n, string); ok:=1; for k from 1 to q do if ok=1 then if searchtext(a, convert(k^n, string))>0 then b:=convert(k, string);

for j from 1 to q do if searchtext(b, convert(n^k, string))>0 then print(k); ok:=0; break; fi; od; fi; fi; od; od; end: P(10^3);

MATHEMATICA

Table[k = 1; While[Or[Length@ SequencePosition[IntegerDigits[k^n], IntegerDigits[n]] == 0, Length@ SequencePosition[IntegerDigits[n^k], IntegerDigits[k]] == 0], k++]; k, {n, 120}] (* Michael De Vlieger, Sep 28 2016, Version 10.1 *)

CROSSREFS

Cf. A061280.

Sequence in context: A272683 A037934 A034086 * A248477 A051050 A267198

Adjacent sequences:  A277076 A277077 A277078 * A277080 A277081 A277082

KEYWORD

nonn,base,easy

AUTHOR

Paolo P. Lava, Sep 28 2016

STATUS

approved

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Last modified February 21 04:43 EST 2018. Contains 299389 sequences. (Running on oeis4.)