cp's OEIS Frontend

A377472 First differences of Colombian or self numbers A003052.

%I A377472 #18 May 02 2025 01:30:27
%S A377472 2,2,2,2,11,11,11,11,11,11,11,11,11,2,11,11,11,11,11,11,11,11,11,2,11,
%T A377472 11,11,11,11,11,11,11,11,2,11,11,11,11,11,11,11,11,11,2,11,11,11,11,
%U A377472 11,11,11,11,11,2,11,11,11,11,11,11,11,11,11,2,11,11,11,11,11,11,11,11,11,2,11,11,11,11,11,11,11,11,11,2,11,11,11,11,11,11,11,11,11,2,11,11,11,11,11,11,11,11,15,11
%N A377472 First differences of Colombian or self numbers A003052.
%C A377472 Most terms are equal to 11.
%C A377472 Up to a(103) = 15, the only exceptions are a(n) = 2 for n = 1, 2, 3, 4, 14, 24, ..., 94.
%C A377472 Then a(n) = 2 for n = 112, 122, ..., 192, and a(201) = 15.
%C A377472 Then a(n) = 2 for n = 210, 220, ..., 290, and a(299) = 15.
%C A377472 This pattern repeats 8 times, with a(n) = 15 for n = 397, 495, ..., 887.
%C A377472 Then a(984) = 28, after which the previous pattern resumes, with a(n) = 2 for n = 992, 1002, ..., 1072, then a(n) = 15 for n = 1081, 1179, ..., 1865.
%C A377472 This larger pattern continues with a(n) = 28 for n = 1962, 2940, 3918, ..., 8808.
%C A377472 A still larger pattern starts at a(9785) = 41, after which the previous pattern repeats with a(9881) = 15, later a(10762) = 28 etc.
%H A377472 Daniel Mondot, <a href="/A377472/b377472.txt">Table of n, a(n) for n = 1..10000</a>
%F A377472 a(n) = A003052(n+1) - A003052(n).
%F A377472 a(n) = A163139(n) + 1 = A163128(n+1) - A163128(n) + 1. - _Max Alekseyev_, Jan 02 2025
%o A377472 (PARI) A377472_upto(N=99)={my(o,L=List()); for(n=1+o=1,oo,if(is_A003052(n), listput(L,n-o); o=n; #L<N||break));L}
%Y A377472 Cf. A003052 (Colombian or self numbers), A377473 (range of this sequence), A377474 (indices where new terms appear), A163128, A163139.
%K A377472 nonn
%O A377472 1,1
%A A377472 _M. F. Hasler_, Oct 29 2024