cp's OEIS Frontend

A121280 Position where concatenate(1,...,n) occurs for the first time in the decimals of Pi (where 3, 1, 4,... are at position 0, 1, 2,...).

%I A121280 #37 Jan 29 2020 04:40:38
%S A121280 1,148,1924,13807,49702,2458885,9470344,186557266,523551502,
%T A121280 191278379839,4368196101671
%N A121280 Position where concatenate(1,...,n) occurs for the first time in the decimals of Pi (where 3, 1, 4,... are at position 0, 1, 2,...).
%C A121280 This sequence uses the same convention for the "position" as sequences A035117, A050279 - A050287, A048940, A096755 - A096763, while A068987(n) = a(n)+1 counts the positions of 3,1,4,.... as 1,2,3,... - _M. F. Hasler_, Mar 18 2017
%C A121280 a(10) > 2*10^9. - _M. F. Hasler_, Apr 13 2019
%C A121280 a(12) > 22*10^12. - _Dmitry Petukhov_, Jan 29 2020
%H A121280 Dave G. Andersen, <a href="http://www.angio.net/pi/">The Pi-Search Page</a>
%H A121280 Subidiom.com, <a href="http://www.subidiom.com/pi">Irrational numbers search engine: π = 3.14159...</a>
%H A121280 Peter Trüb, <a href="https://pi2e.ch/blog/2017/03/10/pi-digits-download/">22.4 trillion digits of pi</a>
%F A121280 a(n) = A068987(n) - 1.
%Y A121280 First occurrence of n times the same digit: A035117 (n '1's), A050281 (n '2's), A050282, A050283, A050284, A050286, A050287, A048940 (n '9's).
%Y A121280 First occurrence of exactly n times the same digit: A096755 (exactly n '1's), A096756, A096757, A096758, A096759, A096760, A096761, A096762, A096763 (exactly n '9's), A050279 (exactly n '0's).
%Y A121280 Cf. A176341: first occurrence of n; A121280 = A068987 - 1: first occurrence of concatenate(1,...,n).
%Y A121280 Cf. A000796: Decimal expansion (or digits) of Pi.
%K A121280 nonn,base,more
%O A121280 1,2
%A A121280 _Alexander R. Povolotsky_, Nov 03 2007
%E A121280 New definition and cross-references from _M. F. Hasler_, Mar 18 2017
%E A121280 Additional term a(9), using subidiom search engine, from _M. F. Hasler_, Apr 13 2019
%E A121280 a(10)-a(11) from _Dmitry Petukhov_, Jan 16 2020