This site is supported by donations to The OEIS Foundation.



Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A034791 a(n) is square mod a(i), i < n. 3


%S 1,2,7,14,31,62,113,226,233,466,647,1294,1487,2974,4919,6329,7951,

%T 12658,15902,26329,26833,47737,52658,53623,53666,95474,107246,128959,

%U 135697,142327,271394,284654,715177,1312777,1430354,1474657,2625554

%N a(n) is square mod a(i), i < n.

%C Apparently A034698 is a subsequence and all elements are products of elements of A034698.

%C a(n) is the smallest integer larger than a(n-1) such that all a(i), 1<=i<n, are quadratic residues mod a(n). - _R. J. Mathar_, Jul 27 2015

%p A034791 := proc(n)

%p option remember;

%p local a,wrks ;

%p if n = 1 then

%p 1;

%p else

%p for a from procname(n-1)+1 do

%p wrks := true;

%p for i from 1 to n-1 do

%p if numtheory[quadres](procname(i),a) <> 1 then

%p wrks := false;

%p end if;

%p end do;

%p if wrks then

%p return a;

%p end if;

%p end do:

%p end if;

%p end proc: # _R. J. Mathar_, Jul 27 2015

%o (Haskell)

%o a034791 n = a034791_list !! (n-1)

%o a034791_list = 1 : f [2..] [1] where

%o f (x:xs) ys | and $ map (flip isSquMod x) ys = x : f xs (x:ys)

%o | otherwise = f xs ys

%o isSquMod u v = u `mod` v `elem` (map ((`mod` v) . (^ 2)) [0..v-1])

%o -- _Reinhard Zumkeller_, fixed Jul 29 2015, Mar 28 2012

%Y Cf. A034698.

%Y Cf. A034793, A034903.

%K nonn

%O 1,2

%A _David W. Wilson_

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified December 3 07:27 EST 2016. Contains 278698 sequences.