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A226186 Composite numbers with both additive and multiplicative digital roots prime. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..47.

EXAMPLE

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

MATHEMATICA

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

CROSSREFS

Cf. A028835, A028843.

Sequence in context: A085926 A071263 A241503 * A325301 A219542 A137480

Adjacent sequences:  A226183 A226184 A226185 * A226187 A226188 A226189

KEYWORD

nonn,base

AUTHOR

Jayanta Basu, Jun 03 2013

STATUS

approved

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Last modified October 20 20:24 EDT 2019. Contains 328273 sequences. (Running on oeis4.)