A204521 - OEIS

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

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OFFSET

1,5

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.

LINKS

Table of n, a(n) for n=1..26.

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

PROG

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

CROSSREFS

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

Sequence in context: A129285 A051440 A101932 * A073313 A374311 A217248

Adjacent sequences: A204518 A204519 A204520 * A204522 A204523 A204524

KEYWORD

nonn

AUTHOR

M. F. Hasler, Jan 15 2012

STATUS

approved