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A144967 Semiprimes n such that n + 1 is divisible by the sum of decimal digits of n. 2
10, 14, 34, 65, 143, 215, 299, 362, 454, 458, 545, 655, 671, 689, 799, 917, 922, 923, 943, 1003, 1007, 1042, 1055, 1111, 1154, 1199, 1253, 1273, 1379, 1507, 1529, 1739, 1807, 1835, 1919, 1957, 2045, 2095, 2183, 2209, 2231, 2279, 2302, 2326, 2342, 2435 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
14 and 15 are semiprimes. 14+1 = 15 is divisible by 1+4 = 5, hence 14 is in the sequence; 15+1 = 16 is not divisible by 1+5 = 6, hence 15 is not in the sequence. - Klaus Brockhaus, Sep 29 2008
MATHEMATICA
Select[Range[5000], Sum[FactorInteger[ # ][[i, 2]], {i, 1, Length[FactorInteger[ # ]]}] == 2 && Mod[ # + 1, Plus @@ IntegerDigits[ # ]] == 0 &] (* Stefan Steinerberger, Sep 29 2008 *)
CROSSREFS
Cf. A001358 (semiprimes). - Klaus Brockhaus, Sep 29 2008
Sequence in context: A164765 A116955 A192291 * A328635 A260564 A107126
KEYWORD
base,nonn
AUTHOR
Giovanni Teofilatto, Sep 27 2008
EXTENSIONS
Corrected and extended by Stefan Steinerberger and Klaus Brockhaus, Sep 29 2008
STATUS
approved

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Last modified March 29 02:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)