A108662 - OEIS

%I #24 Jan 09 2019 03:20:59

%S 11,12,14,16,21,23,25,27,32,38,41,45,49,52,54,56,58,61,65,72,78,83,85,

%T 87,94,101,102,104,106,110,111,113,119,120,126,131,133,137,140,146,

%U 159,160,162,164,166,168,173,179,186,191,195,197,199,201,203,205,207,210

%N Numbers whose sum of squares of digits is a prime.

%C 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.

%C 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

%H Harvey Dale and Zak Seidov, <a href="/A108662/b108662.txt">Table of n, a(n) for n = 1..10000</a> [First 1000 terms from Harvey Dale]

%e 23 is in the sequence because 2^2 + 3^2 = 13 is a prime.

%t Select[Range[300],PrimeQ[Total[IntegerDigits[#]^2]]&] (* _Harvey P. Dale_, May 25 2012 *)

%o (PARI) isok(n) = isprime(norml2(digits(n))); \\ _Michel Marcus_, Jan 09 2019

%Y Cf. A003132, A009994, A052034, A234021.

%K nonn,base

%O 1,1

%A _Zak Seidov_, Jun 16 2005