A072021 Smallest solution to gcd(x, reverse(x)) = 5^n.

5, 5200, 521000, 5213750, 521875, 5218750, 52130234375, 5734841796875, 57869714843750, 526046650390625, 5265674365234375, 52187008544921875, 526515306396484375, 5213023309008789062500, 5213596736358642578125, 5260466086273193359375, 526041911745452880859375

Offset

1,1

Links

Hiroaki Yamanouchi, Table of n, a(n) for n = 1..25

Formula

a(n) = A069554(5^n).

Example

For n = 4, gcd(521875, 578125) = 3125 = 5^4.
For n = 8, a(8) = 5734841796875 = 5^9*2936239, reverse(a(8)) = 5786971484375 = 5^8*71*208657.

Prog

(PARI) a(n) = {my(k = 1); while (gcd(k, fromdigits(Vecrev(digits(k)))) != 5^n, k++); k; } \\ Michel Marcus, Jul 13 2018

Crossrefs

Cf. A004086, A055483, A069554, A071686, A072005, A072050, A072016-A072018.

Sequence in context: A357125 A086896 A177503 * A196627 A013535 A079812

Adjacent sequences: A072018 A072019 A072020 * A072022 A072023 A072024

Keyword

nonn,base

Author

Labos Elemer, Jun 06 2002

Extensions

a(9)-a(18) from Hiroaki Yamanouchi, Sep 10 2014

Status

approved