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 A225864 Composite numbers for which both sum and product of digits are primes. 1
 12, 21, 115, 511, 1112, 1121, 1211, 11711, 13111, 17111, 31111, 71111, 111112, 121111, 211111, 1111115, 1111117, 1111171, 1111511, 1115111, 1151111, 1511111, 1711111, 5111111, 7111111, 111111115, 111111151, 111111311, 111111511, 111115111, 111131111, 111151111 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Chai Wah Wu, Table of n, a(n) for n = 1..10000 MATHEMATICA d[n_] := IntegerDigits[n]; t={}; Do[If[!PrimeQ[n] && PrimeQ[Plus@@(x=d[n])] && PrimeQ[Times@@x], AppendTo[t, n]], {n, 2*10^6}]; t Select[Range[72*10^5], CompositeQ[#]&&AllTrue[{Total[IntegerDigits[#]], Times@@ IntegerDigits[ #]}, PrimeQ]&] (* The program generates the first 25 terms of the sequence. *) (* Harvey P. Dale, May 24 2024 *) PROG (Python) from __future__ import division from sympy import isprime A225864_list = [] for l in range(1, 20): plist, q = [p for p in [2, 3, 5, 7] if isprime(l-1+p)], (10**l-1)//9 for i in range(l): for p in plist: r = q+(p-1)*10**i if not isprime(r): A225864_list.append(r) # Chai Wah Wu, Aug 15 2017 CROSSREFS Cf. A046713, A225863. Sequence in context: A201015 A044005 A321771 * A134514 A030299 A352991 Adjacent sequences: A225861 A225862 A225863 * A225865 A225866 A225867 KEYWORD nonn,base AUTHOR Jayanta Basu, May 18 2013 EXTENSIONS Extended by T. D. Noe, May 18 2013 STATUS approved

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Last modified August 8 18:48 EDT 2024. Contains 375023 sequences. (Running on oeis4.)