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Search: id:A121614
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| A121614 |
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Numbers n that have composite sum of digits and prime sum of squares of digits. |
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+0
1
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| 27, 45, 54, 72, 78, 87, 126, 159, 162, 168, 186, 195, 207, 216, 234, 243, 249, 261, 267, 270, 276, 294, 324, 342, 348, 357, 375, 384, 405, 423, 429, 432, 438, 450, 483, 492, 504, 519, 537, 540, 573, 591, 612, 618, 621, 627, 672, 678, 681, 687, 702, 708, 720
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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For example: the sum of digits of 27 is 9 which is composite; the sum of squares of digits of 27 is 53 which is prime.
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MATHEMATICA
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sod[k_, m_] := Plus @@ (IntegerDigits[k]^m); Select[ Table[n, {n, 1000}], (! PrimeQ[sod[ #, 1]] && PrimeQ[sod[ #, 2]]) &]
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CROSSREFS
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Cf. A091362 (Primes p such that the sum of the digits of p is not prime, but the sum of the squares of the digits of p is prime) is a prime subsequence of this sequence.
Sequence in context: A124940 A114446 A141229 this_sequence A046340 A046316 A046373
Adjacent sequences: A121611 A121612 A121613 this_sequence A121615 A121616 A121617
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KEYWORD
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base,nonn
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AUTHOR
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Tanya Khovanova (tanyakh(AT)yahoo.com), Sep 08 2006
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