A072969 Least k > 0 such that the last digit of k^n is the same as the last digit of n^k.

1, 2, 3, 2, 5, 4, 7, 4, 9, 10, 1, 4, 7, 4, 5, 2, 3, 2, 9, 10, 1, 2, 3, 2, 5, 4, 7, 4, 9, 10, 1, 4, 7, 4, 5, 2, 3, 2, 9, 10, 1, 2, 3, 2, 5, 4, 7, 4, 9, 10, 1, 4, 7, 4, 5, 2, 3, 2, 9, 10, 1, 2, 3, 2, 5, 4, 7, 4, 9, 10, 1, 4, 7, 4, 5, 2, 3, 2, 9, 10, 1, 2, 3, 2, 5, 4, 7, 4, 9, 10, 1, 4, 7, 4, 5, 2, 3, 2, 9

Offset

1,2

Links

Table of n, a(n) for n=1..99.

Formula

a(n) is a periodic sequence with period (1, 2, 3, 2, 5, 4, 7, 4, 9, 10, 1, 4, 7, 4, 5, 2, 3, 2, 9, 10, ) of length 20

Prog

(PARI) a(n)=if(n<0, 0, k=1; while(abs(k^n%10-n^k%10)>0, s++); s)

Crossrefs

Sequence in context: A365099 A342694 A212831 * A139712 A175856 A075365

Adjacent sequences: A072966 A072967 A072968 * A072970 A072971 A072972

Keyword

base,easy,nonn

Author

Benoit Cloitre, Aug 13 2002

Status

approved