A226186 Composite numbers with both additive and multiplicative digital roots prime.

12, 21, 34, 57, 75, 115, 232, 299, 322, 371, 376, 398, 511, 579, 597, 637, 713, 731, 736, 759, 763, 795, 893, 938, 957, 975, 992, 1112, 1121, 1137, 1157, 1173, 1175, 1211, 1299, 1317, 1355, 1371, 1389, 1398, 1469, 1474, 1496, 1517, 1535, 1649, 1694

Offset: 1

Author

Jayanta Basu, Jun 03 2013

Keywords

• nonn
• base

Examples

			322 is here since for 322 additive digital root is 7 and multiplicative digital root is 2, both are primes.
		

Crossrefs

Cf. A028835, A028843.

Programs

Mathematica

a[n_] := NestWhile[Times@@IntegerDigits[#]&, n, #>9&]; Select[Range[1700], !PrimeQ[#] && And@@PrimeQ[{a[#], Mod[#,9]}]&]