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A121614 Numbers n that have composite sum of digits and prime sum of squares of digits. 1
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; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

EXAMPLE

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.

MATHEMATICA

sod[k_, m_] := Plus @@ (IntegerDigits[k]^m); Select[ Table[n, {n, 1000}], (! PrimeQ[sod[ #, 1]] && PrimeQ[sod[ #, 2]]) &]

CROSSREFS

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: A141229 A253919 A259504 * A046340 A046316 A046373

Adjacent sequences:  A121611 A121612 A121613 * A121615 A121616 A121617

KEYWORD

base,nonn

AUTHOR

Tanya Khovanova, Sep 08 2006

STATUS

approved

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Last modified May 23 02:46 EDT 2017. Contains 286909 sequences.