

A104377


Number of distinct prime divisors of numbers derived from three consecutive concatenated odd numbers.


2



2, 3, 2, 2, 3, 4, 2, 3, 3, 2, 4, 2, 2, 2, 2, 4, 3, 3, 2, 2, 4, 3, 3, 3, 2, 5, 3, 2, 3, 3, 3, 3, 2, 2, 2, 3, 2, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 4, 2, 4, 4, 4, 3, 3, 4, 2, 3, 4, 3, 4, 3, 3, 3, 3, 5, 3, 4, 2, 2, 6, 3, 3, 4, 3, 3, 3, 3, 3, 3, 3, 5, 3, 4, 4, 4, 5
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OFFSET

1,1


LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000


EXAMPLE

The number of distinct prime divisors of 135 is 2  the first term in the sequence.
The number of distinct prime divisors of 357 is 3  the second term in the sequence.
The number of distinct prime divisors of 579 is 2  the third term in the sequence.


MAPLE

read("transforms") :
A104377 := proc(n) digcat2(digcat2(2*n+1, 2*n+3), 2*n+5) ; nops(numtheory[factorset](%)) ; end proc: # R. J. Mathar, Feb 03 2011


MATHEMATICA

a[n_] := PrimeNu@ FromDigits@(Join @@ IntegerDigits /@ (2*n + {1, 1, 3})); Array[a, 100] (* Amiram Eldar, Jan 27 2020 *)


CROSSREFS

Cf. A001221, A104186.
Sequence in context: A079643 A329317 A118480 * A109337 A303539 A303540
Adjacent sequences: A104374 A104375 A104376 * A104378 A104379 A104380


KEYWORD

nonn,base


AUTHOR

Parthasarathy Nambi, Apr 16 2005


EXTENSIONS

Offset corrected and more terms added by Amiram Eldar, Jan 27 2020


STATUS

approved



