cp's OEIS Frontend

A230956 Semiprimes k with a semiprime number of syllables in their name in American English.

%I A230956 #19 May 27 2024 22:38:44
%S A230956 57,74,87,106,111,121,122,123,129,133,134,141,142,143,145,146,155,158,
%T A230956 159,161,166,169,183,185,194,201,202,203,205,206,209,217,221,226,235,
%U A230956 249,253,254,259,262,265,289,291,295,298,299,301,302,303,305,309
%N A230956 Semiprimes k with a semiprime number of syllables in their name in American English.
%C A230956 This is to A163648 as semiprimes A001358 are to primes A000040.
%C A230956 The word "and" is excluded, 101 is "one hundred one" rather than "one hundred and one."
%C A230956 Number of syllables in n in American English is A075774.
%C A230956 See A231073 and A231075 for prime analogs counting words respectively letters.
%H A230956 Charles R Greathouse IV, <a href="/A230956/b230956.txt">Table of n, a(n) for n = 1..10000</a>
%F A230956 {k: k is in A001358 and A075774(k) is in A001358}.
%e A230956 87 is in the sequence because 87 = 3 * 29 is semiprime, "eighty-seven" has 4 syllables, and 4 = 2^2 is also semiprime.
%e A230956 106 is in the sequence because 106 = 2 * 53 is semiprime and "one hundred six" has semiprime 4 syllables.
%e A230956 111 is in the sequence because 111 = 3 * 37 is semiprime and "one hundred eleven" has semiprime 6 = 2*3 syllables.
%o A230956 (Python) # uses function in A075774
%o A230956 from sympy import factorint
%o A230956 def issemiprime(n): return sum(factorint(n).values()) == 2
%o A230956 def ok(n): return issemiprime(A075774(n)) and issemiprime(n)
%o A230956 print([k for k in range(310) if ok(k)]) # _Michael S. Branicky_, May 27 2024
%Y A230956 Cf. A001358, A075774, A163648, A231073, A231075.
%K A230956 nonn,word,easy
%O A230956 1,1
%A A230956 _Jonathan Vos Post_, Nov 04 2013
%E A230956 Corrected and extended by _Charles R Greathouse IV_, Jan 23 2014