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Numbers k such that floor(k/10)^(k mod 10) contains the digit (k mod 10).
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%I #15 Dec 23 2024 14:53:46

%S 11,26,37,39,46,52,55,56,57,59,66,67,69,73,74,76,78,84,86,87,95,97,99,

%T 101,111,112,113,114,115,116,117,118,119,121,128,129,131,136,137,138,

%U 139,141,144,145,146,148,151,152,153,155,156,157,158,159,161,162,165,166,169,171,172,173,175

%N Numbers k such that floor(k/10)^(k mod 10) contains the digit (k mod 10).

%C Or: Numbers k such that A059995(k)^A010879(k) contains the last digit of k, A010879(k).

%C It's easy to see that all numbers ending in {11, 37, 46, 52, 55, 59, 66, 69, 73, 97, 99} are in the sequence: for these, A059995(k)^A010879(k) mod 100 = (1, 87, 96, 25, 25, 25, 56, 96, 43, 69, 89).

%H M. F. Hasler, in reply to Éric Angelini, <a href="https://web.archive.org/web/*/http://list.seqfan.eu/oldermail/seqfan/2019-November/020192.html">2019 must be read here as 201^9</a>, SeqFan list, Nov. 21, 2019.

%o (PARI) select( t->setsearch(Set(digits((t\10)^(t%10))),t%10),[0..9999])

%Y Cf. A059995 (floor(n/10): drop final digit), A010879 (n mod 10; final digit of n).

%K nonn,base

%O 1,1

%A _Eric Angelini_ and _M. F. Hasler_, Nov 21 2019