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%I #34 Nov 12 2021 10:22:02
%S 11,12,22,31,41,52,61,62,71,72,81,82,92,101,112,121,122,131,142,151,
%T 152,162,172,181,191,192,202,211,212,232,241,242,251,262,271,272,273,
%U 281,292,302,311,331,332,352,361,362,382,392,401,412,421,422,431,432,452
%N Numbers whose last digit is the number of their distinct prime factors.
%C All prime numbers whose last digit is 1 have this property.
%C Only numbers with at most 9 distinct prime factors appear in this sequence.
%H Michael S. Branicky, <a href="/A331194/b331194.txt">Table of n, a(n) for n = 1..10000</a>
%e 272 is such a number because 272 = 2^4 * 17. It has 2 distinct prime factors {2,17} and its last digit is 2.
%t Select[Range@500,Last@IntegerDigits@#==PrimeNu@#&]
%t Select[Range[500],PrimeNu[#]==NumberDigit[#,0]&] (* _Harvey P. Dale_, Aug 12 2021 *)
%o (PARI) isok(m) = omega(m) == (m % 10); \\ _Michel Marcus_, Feb 24 2020
%o (Python)
%o from sympy import factorint
%o def ok(n): return n > 1 and n%10 == len(factorint(n))
%o print([k for k in range(460) if ok(k)]) # _Michael S. Branicky_, Nov 12 2021
%Y Cf. A001221 (omega), A010879 (final digit of n).
%K nonn,base
%O 1,1
%A _Giorgos Kalogeropoulos_, Feb 23 2020
%E a(49) and beyond from _Michael S. Branicky_, Nov 12 2021
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