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A252794 Numbers m such that 9^m + m is a semiprime. 1
1, 5, 68, 85, 86, 92, 136 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(8) > 435. - Carl Schildkraut, Aug 14 2015

LINKS

Table of n, a(n) for n=1..7.

EXAMPLE

1 is in this sequence because 9^1+1 = 2*5 is semiprime.

5 is in this sequence because 9^5+5 = 2*29527 and these two factors are prime.

MATHEMATICA

Select[Range[435], PrimeOmega[9^# + #]==2 &]

PROG

(MAGMA) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [m: m in [1..435] | IsSemiprime(s) where s is 9^m+m];

CROSSREFS

Cf. similar sequences listed in A252788.

Cf. A252662.

Sequence in context: A207979 A129963 A115764 * A328359 A003361 A336433

Adjacent sequences:  A252791 A252792 A252793 * A252795 A252796 A252797

KEYWORD

nonn,more

AUTHOR

Vincenzo Librandi, Dec 27 2014

EXTENSIONS

a(4)-a(7) from Carl Schildkraut, Aug 14 2015

STATUS

approved

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Last modified December 3 16:20 EST 2020. Contains 338906 sequences. (Running on oeis4.)