A115305 a(n) = if n<5 then n else 5*a(floor(n/5)) + 4 - n mod 5.

1, 2, 3, 4, 9, 8, 7, 6, 5, 14, 13, 12, 11, 10, 19, 18, 17, 16, 15, 24, 23, 22, 21, 20, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52

Offset: 1

Author

Reinhard Zumkeller, Jan 20 2006

Keywords

• nonn
• base

Comments

Self-inverse permutation of the natural numbers;

A115310(n+3,4) = a(n);

if n is written in base 5 representation, then a(n) is the value after replacing all digits d (but not the leading one) by 4-d.

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

Cf. A054429, A115303, A115304, A115306, A115307, A115308, A115309, A106649.

Programs

Mathematica

Table[d = IntegerDigits[n, 5]; FromDigits[Prepend[4 - Rest@d, d[[1]]], 5], {n, 72}] (* Ivan Neretin, Apr 26 2017 *)