login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A048646 Primes p such that the decimal digits of p^2 can be partitioned into two or more nonzero squares. 5
7, 13, 19, 37, 41, 107, 191, 223, 379, 487, 997, 1063, 1093, 1201, 1301, 1907, 2029, 3019, 3169, 3371, 5081, 5099, 5693, 6037, 9041, 9619, 9721, 9907, 10007, 11681, 12227, 12763, 17393, 18493, 19013, 19213, 19219, 21059, 21157, 21193, 25931 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
7 is present because 7^2=49 can be partitioned into two squares 4 and 9; 13^2 = 169 = 16_9; 37^2 = 1369 = 1_36_9.
997^2 = 994009 = 9_9_400_9, 1063^2 = 1129969 = 1_12996_9, 997 and 1063 are primes, so 997 and 1063 are in the sequence.
PROG
(Haskell)
a048646 n = a048646_list !! (n-1)
a048646_list = filter ((== 1) . a010051') a048653_list
-- Reinhard Zumkeller, Apr 17 2015
(Python)
from math import isqrt
from sympy import primerange
def issquare(n): return isqrt(n)**2 == n
def ok(n, c):
if n%10 in {2, 3, 7, 8}: return False
if issquare(n) and c > 1: return True
d = str(n)
for i in range(1, len(d)):
if d[i] != '0' and issquare(int(d[:i])) and ok(int(d[i:]), c+1):
return True
return False
def aupto(lim): return [p for p in primerange(1, lim+1) if ok(p*p, 1)]
print(aupto(25931)) # Michael S. Branicky, Jul 10 2021
CROSSREFS
Cf. A048375.
Cf. A010051, intersection of A048653 and A000040.
Sequence in context: A108295 A071923 A344045 * A152087 A098059 A078860
KEYWORD
nice,nonn,base
AUTHOR
EXTENSIONS
Corrected and extended by Naohiro Nomoto, Sep 01 2001
"Nonzero" added to definition by N. J. A. Sloane, May 08 2021
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 19 01:22 EDT 2024. Contains 370952 sequences. (Running on oeis4.)