

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.


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
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

The primes fitting exactly in a "Primesdigits square" are given by A158024. Terms computed by JeanMarc Falcoz.


LINKS

Robert Israel, Table of n, a(n) for n = 1..3000
Eric Angelini, Digit Spiral
E. Angelini, Digit Spiral [Cached copy, with permission]


EXAMPLE

...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 side3 square with this property. The next properly filled square will have side 6.


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


CROSSREFS

Sequence in context: A121538 A339508 A275844 * A216345 A026510 A138204
Adjacent sequences: A158022 A158023 A158024 * A158026 A158027 A158028


KEYWORD

base,nonn


AUTHOR

Eric Angelini, Mar 11 2009


STATUS

approved



