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 A244748 Numbers k such that (product of digits of k)^2 + 1 is prime. 2
 1, 2, 4, 6, 11, 12, 14, 16, 21, 22, 23, 25, 27, 28, 32, 38, 41, 44, 45, 46, 49, 52, 54, 58, 61, 64, 66, 69, 72, 78, 82, 83, 85, 87, 94, 96, 111, 112, 114, 116, 121, 122, 123, 125, 127, 128, 132, 138, 141, 144, 145, 146, 149, 152, 154, 158, 161, 164, 166, 169, 172, 178, 182, 183 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A number k is a term of this sequence iff A007954(k)^2 is in A006093. This sequence is infinite. With any number a(n), you can add infinitely many 1's to its decimal representation. E.g., 85 is in this sequence, so 185, 815, 851, 1185, 1815, 18115, etc. are terms as well. LINKS Jens Kruse Andersen, Table of n, a(n) for n = 1..10000 EXAMPLE (7*2)^2 + 1 = 197 is prime. Thus 72 is a term of this sequence. PROG (PARI) for(n=1, 10^3, d=digits(n); if(ispseudoprime(prod(i=1, #d, d[i])^2+1), print1(n, ", "))) CROSSREFS Cf. A081988, A007954. Sequence in context: A097954 A324333 A081988 * A245017 A300149 A171921 Adjacent sequences:  A244745 A244746 A244747 * A244749 A244750 A244751 KEYWORD nonn,base,easy AUTHOR Derek Orr, Jul 12 2014 EXTENSIONS Corrected by Jens Kruse Andersen, Jul 13 2014 STATUS approved

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Last modified September 24 14:00 EDT 2020. Contains 337321 sequences. (Running on oeis4.)