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%I #14 Jul 20 2019 14:19:04
%S 15,21,26,40,57,62,80,85,86,91,93,111,114,124,129,133,146,170,171,172,
%T 183,215,219,222,228,242,259,266,285,292,312,314,333,341,343,365,366,
%U 381,399,422,438,444,455,468,471,482,507,518,532,549,553
%N Non-oblong composites m such that beta(m) = tau(m)/2 where beta(m) is the number of Brazilian representations of m and tau(m) is the number of divisors of m.
%C As tau(m) = 2 * beta(m), the terms of this sequence are not squares.
%C The number of Brazilian representations of a non-oblong number m with repdigits of length = 2 is beta'(n) = tau(n)/2 - 1.
%C This sequence is the first subsequence of A326380: non-oblong composites which have only one Brazilian representation with three digits or more.
%H <a href="https://oeis.org/wiki/Index_to_OEIS:_Section_Br#Brazilian_numbers">Index entries for sequences related to Brazilian numbers</a>
%e tau(m) = 4 and beta(m) = 2 for m = 15, 21, 26, 57, 62, 85, 86, ... with 15 = 1111_2 = 33_4.
%e tau(m) = 8 and beta(m) = 4 for m = 40 = 1111_3 = 55_7 = 44_9 = 22_19.
%e tau(m) = 10 and beta(m) = 5 for m = 80 = 2222_3 = 88_9 = 55_15 = 44_19 = 22_39.
%o (PARI) isoblong(n) = my(m=sqrtint(n)); m*(m+1)==n; \\ A002378
%o beta(n) = sum(i=2, n-2, #vecsort(digits(n, i), , 8)==1); \\ A220136
%o isok(m) = !isprime(m) && !isoblong(m) && (beta(m) == numdiv(m)/2); \\ _Michel Marcus_, Jul 15 2019
%Y Cf. A000005 (tau), A220136 (beta).
%Y Subsequence of A167782, A308874 and A326380.
%Y Cf. A326386 (non-oblongs with tau(m)/2 - 1), A326388 (non-oblongs with tau(m)/2 + 1), A326389 (non-oblongs with tau(m)/2 + 2).
%K nonn,base
%O 1,1
%A _Bernard Schott_, Jul 14 2019
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