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

0,3

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.

Links

Table of n, a(n) for n=0..24.

Example

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.

Prog

(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

Crossrefs

Cf. A064532.

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

Sequence in context: A237375 A237368 A017078 * A236055 A236048 A235954

Adjacent sequences: A359242 A359243 A359244 * A359246 A359247 A359248

Keyword

nonn,base

Author

Bernard Schott, Dec 22 2022

Extensions

More terms from Rémy Sigrist, Dec 22 2022

Status

approved