A244863 Semiprimes whose digit sum is a perfect square.

4, 9, 10, 22, 121, 169, 178, 187, 202, 259, 295, 301, 358, 394, 466, 493, 529, 538, 565, 583, 655, 718, 745, 763, 781, 799, 817, 835, 862, 871, 889, 898, 934, 943, 961, 979, 1003, 1111, 1159, 1177, 1186, 1195, 1267, 1285, 1294, 1339, 1357, 1366, 1393, 1438, 1465

Offset: 1

Author

K. D. Bajpai, Jul 07 2014

Keywords

• nonn
• base

Comments

Subsequence of A028839.

Examples

			178 is in the sequence because 178 = 2*89 (semiprime) and 1+7+8 = 16 (square).
187 is in the sequence because 187 = 11*17 (semiprime) and 1+8+7 = 16 (square).
		

Links

• K. D. Bajpai, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A007953, A028839, A048519.

Cf. A107288 (Primes whose digit sum is square).

Programs

Maple

select(n -> numtheory:-bigomega(n)=2 and issqr(convert(convert(n,base,10),`+`)),
[$1..3000]); # Robert Israel, Jul 09 2014

Mathematica

Select[Range[3000], PrimeOmega[#] == 2 && IntegerQ[Sqrt[Apply [Plus, IntegerDigits[#]]]] &]