login
A108662
Numbers whose sum of squares of digits is a prime.
10
11, 12, 14, 16, 21, 23, 25, 27, 32, 38, 41, 45, 49, 52, 54, 56, 58, 61, 65, 72, 78, 83, 85, 87, 94, 101, 102, 104, 106, 110, 111, 113, 119, 120, 126, 131, 133, 137, 140, 146, 159, 160, 162, 164, 166, 168, 173, 179, 186, 191, 195, 197, 199, 201, 203, 205, 207, 210
OFFSET
1,1
COMMENTS
If m is in the sequence, then so are 10*m and any anagram (even with adding zeros between digits) of m. E.g., 12 is a term, hence 21, 102, 120, 201, 10020 all are here.
A sequence of primitive terms is of interest. It starts with 11, 12, 14, 16, 23, 25, 27, 38, 45, 49, 56, 58, 78, 111, 113, 119, 126, 133, 137, 146, 159, 166, 168, 179, 199. Note that digits are in nondecreasing order. - Zak Seidov, Dec 31 2013
LINKS
Harvey Dale and Zak Seidov, Table of n, a(n) for n = 1..10000 [First 1000 terms from Harvey Dale]
EXAMPLE
23 is in the sequence because 2^2 + 3^2 = 13 is a prime.
MATHEMATICA
Select[Range[300], PrimeQ[Total[IntegerDigits[#]^2]]&] (* Harvey P. Dale, May 25 2012 *)
PROG
(PARI) isok(n) = isprime(norml2(digits(n))); \\ Michel Marcus, Jan 09 2019
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Zak Seidov, Jun 16 2005
STATUS
approved