A158025 Sides of squares which are filled exactly (no holes, no overlaps) by the digits needed to write a subsequence of consecutive Primes starting with 2.
1, 2, 4, 6, 7, 8, 10, 11, 13, 14, 16, 17, 19, 20, 72, 73, 77, 78, 82, 83, 87, 88, 92, 93, 97, 98, 102, 103, 107, 108, 112, 113, 117, 118, 122, 123, 127, 128, 132, 133, 137, 138, 142, 143, 147, 148, 152, 153, 157, 158, 162, 163, 167, 168, 172, 173, 177, 178, 182, 183
Offset: 1
Examples
...2...23...2357 .......57...1113 ............1719 ............2329 The above squares, filled exactly by a subsequence of consecutive primes starting with 2 have sides 1, 2, 4. There is no side-3 square with this property. The next properly filled square will have side 6.
Links
- Robert Israel, Table of n, a(n) for n = 1..3000
- Eric Angelini, Digit Spiral
- E. Angelini, Digit Spiral [Cached copy, with permission]
Programs
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Maple
X:= 0: p:= 1: Res:= NULL: count:= 0: while count < 100 do p:= nextprime(p); X:= X + ilog10(p) + 1; if issqr(X) then Res:= Res,sqrt(X); count:= count+1: fi od: Res; # Robert Israel, Jan 13 2020
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