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A244863 Semiprimes whose digit sum is a perfect square. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Subsequence of A028839.
LINKS
EXAMPLE
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).
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[#]]]] &]
CROSSREFS
Cf. A107288 (Primes whose digit sum is square).
Sequence in context: A177927 A062398 A030754 * A077584 A093896 A332449
KEYWORD
nonn,base
AUTHOR
K. D. Bajpai, Jul 07 2014
STATUS
approved

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Last modified July 13 18:16 EDT 2024. Contains 374285 sequences. (Running on oeis4.)