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 A104186 Number of distinct prime divisors of numbers from four consecutive concatenated odd numbers. 2
 2, 2, 2, 2, 3, 3, 3, 2, 2, 4, 2, 1, 3, 3, 2, 2, 3, 2, 2, 4, 3, 2, 4, 2, 2, 3, 3, 4, 4, 3, 2, 4, 3, 2, 5, 2, 2, 4, 1, 3, 3, 4, 2, 3, 3, 2, 3, 3, 3, 4, 3, 3, 2, 3, 5, 3, 3, 1, 4, 4, 2, 4, 2, 2, 5, 2, 4, 3, 3, 3, 3, 4, 2, 4, 3, 2, 3, 2, 2, 3, 4, 3, 3, 2, 3, 6, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Interestingly, 23252729 is prime. LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE The number of distinct prime factors of 1357 is 2 - the first term in the sequence. The number of distinct prime factors of 3579 is 2 - the second term in the sequence. The number of distinct prime factors of 57911 is 2 - the third term in the sequence. MATHEMATICA a[n_] := PrimeNu@ FromDigits @ (Join @@ IntegerDigits /@ (2*n + {-1, 1, 3, 5})); Array[a, 100] (* Amiram Eldar, Jan 27 2020 *) CROSSREFS Cf. A001221, A104377. Sequence in context: A194320 A231555 A120425 * A184320 A092363 A133874 Adjacent sequences:  A104183 A104184 A104185 * A104187 A104188 A104189 KEYWORD nonn,base AUTHOR Parthasarathy Nambi, Apr 16 2005 EXTENSIONS Offset corrected and more terms added by Amiram Eldar, Jan 27 2020 STATUS approved

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Last modified May 5 17:56 EDT 2021. Contains 343572 sequences. (Running on oeis4.)