This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A253785 #9 Jan 16 2015 18:22:49 %S A253785 10,14,20,22,26,28,33,34,38,39,40,44,46,50,51,52,56,57,58,62,66,68,69, %T A253785 70,74,76,78,80,82,86,87,88,92,93,94,98,99,100,102,104,106,110,111, %U A253785 112,114,116,117,118,122,123,124,129,130,132,134,136,138,140,141,142,145,146,148,152,153,154,155,156,158,159,160,164,166,170 %N A253785 Composite numbers n = prime(i_1) * ... * prime(i_k), prime(i_1) <= prime(i_2) <= ... <= prime(i_k), with at least one pair of successive prime factors (when sorted into monotonic order) where the latter prime factor is greater than the square of the former: prime(i_x)^2 < prime(i_{x+1}), for some x in 1 .. k-1, where k = A001222(n) and i_k = A061395(n). %H A253785 Antti Karttunen, <a href="/A253785/b253785.txt">Table of n, a(n) for n = 1..10000</a> %e A253785 10 = 2*5 is present as 2^2 < 5. %e A253785 50 = 2*5*5 is present as 2^2 < 5. %e A253785 51 = 3*17 is present as 3^2 < 17. %e A253785 66 = 2*3*11 is present as 3^2 < 11. %o A253785 (Scheme, with _Antti Karttunen_'s IntSeq-library) %o A253785 (define A253785 (MATCHING-POS 1 1 (lambda (n) (not (numbers-densely-distributed? (ifactor n)))))) %o A253785 (define (numbers-densely-distributed? lista) (cond ((null? lista) #t) ((null? (cdr lista)) #t) ((< (A000290 (car lista)) (cadr lista)) #f) (else (numbers-densely-distributed? (cdr lista))))) %Y A253785 Complement: A253784. %Y A253785 Subsequences: A138511, A253569. %Y A253785 Cf. A000290, A001222, A061395. %Y A253785 Differs from A245729 for the first time at n=14, where a(14) = 50, while A245729(14) = 51. %K A253785 nonn %O A253785 1,1 %A A253785 _Antti Karttunen_, Jan 16 2015