A309697 - OEIS

%I #11 Aug 13 2019 05:34:35

%S 0,0,2,5,2,5,4,1,8,0,1,5,5,1,7,1,7,2,7,7,2,8,6,7,2,7,0,3,6,4,3,7,1,3,

%T 7,3,1,0,5,7,4,6,0,9,2,9,6,5,4,2,5,9,7,5,7,5,5,8,3,7,6,4,4,1,2,1,2,7,

%U 2,4,7,1,3,7,7,7,9,6,1,7,8,2,8,3,2,3,8,9,0,0,9,3,9,9,7,9,3,4,9,0

%N a(n) is the digit that precedes the last nonzero digit of n^n.

%C Chu proves that the constant 0.00252541801... is transcendental.

%H Hung Viet Chu, <a href="https://arxiv.org/abs/1908.03855">New Transcendental Numbers from Certain Sequences</a>, arXiv:1908.03855 [math.NT], 2019.

%t a[n_] := Floor[PowerMod[n/10^IntegerExponent[n, 10], n, 100]/10]; Array[a, 100] (* _Giovanni Resta_, Aug 13 2019 *)

%o (PARI) a(n) = {my(d=digits(n^n)); forstep (k=#d, 1, -1, if (d[k], if (k==1, return (0)); return (d[k-1]));); return(0);}

%Y Cf. A056849.

%K nonn,base

%O 1,3

%A _Michel Marcus_, Aug 13 2019