A359245 The smallest square with exactly n circular loops (or holes) in its decimal expansion (A064532).

1, 0, 81, 289, 1089, 8836, 6889, 80089, 688900, 1868689, 8508889, 29888089, 288898009, 983888689, 3808988089, 8680089889, 86908808809, 488088068689, 878686888689, 2888986888804, 48890888808804, 108506888888896, 88869893888889, 880881089888881, 788088668888889

Offset: 0

Author

Bernard Schott, Dec 22 2022

Keywords

• nonn
• base

Comments

The digit 8 has two loops, the digits 0, 6 and 9 have one loop, and other digits (including 4) have no hole.

Least square k such that A064532(k) = n.

Examples

			a(3) = 289 because 8 has two loops and 9 has one loop for a total of 3, and 289 is the smallest such square.
		

Crossrefs

Cf. A064532.

Similar: A331898 (primes), A337842 (palindromes).

Programs

PARI

a(n) = { for (k=0, oo, my (d=digits(k^2)); if (n==(k==0)+sum(i=1, #d, [1, 0, 0, 0, 0, 0, 1, 0, 2, 1][1+d[i]]), return (k^2))) } \\ Rémy Sigrist, Dec 22 2022

Extensions

More terms from Rémy Sigrist, Dec 22 2022