A204521 Square root of floor(A055812(n) / 5).

0, 0, 0, 1, 3, 4, 8, 21, 55, 72, 144, 377, 987, 1292, 2584, 6765, 17711, 23184, 46368, 121393, 317811, 416020, 832040, 2178309, 5702887, 7465176

Offset: 1

Author

M. F. Hasler, Jan 15 2012

Keywords

• nonn

Comments

Or: Numbers whose square yields another square when written in base 5.

(For the first 3 terms, the above "base 5" interpretation is questionable, since they have only 1 digit in base 5. It is understood that dropping this digit yields 0.)

Base-5 analog of A031150 [base 10], A001353 [base 3], A001542 [base 2].

The square roots of A055812 are listed in A204520.

Crossrefs

Cf. A055792, A055793, A204519, A204517, A204512, A204503 and A023110.

Programs

PARI

b=5;for(n=1,2e9,issquare(n^2\b) && print1(sqrtint(n^2\b),","))

Formula

Empirical g.f.: x^4*(x^5+3*x^4+8*x^3+4*x^2+3*x+1) / ((x^4-4*x^2-1)*(x^4+4*x^2-1)). - Colin Barker, Sep 15 2014