A328724 - OEIS

A328724

a(1)=2, a(2)=3; a(n) is the smallest k > a(n-1) such that k + a(n-1) is a multiple of a(n-2).

2, 3, 5, 7, 8, 13, 19, 20, 37, 43, 68, 104, 168, 248, 256, 488, 536, 928, 1216, 1568, 2080, 2624, 3616, 4256, 6592, 10432, 15936, 25792, 37952, 39424, 74432, 83264, 140032, 193024, 227072, 352000, 556288, 851712, 1373440, 2033408, 2086912, 4013312

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OFFSET

1,1

COMMENTS

(a(n+1)+a(n+2))/a(n) gives the sequence 4, 4, 3, 3, 4, 3, 3, 4, 3, 4, 4, 4, 3, 3, 4, 3, 4, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 3, 3, 4, 3, 4, 3, 3, 4, 4, 4, 4, 3, 3, 4, 3, 4, 3, 3, 3, 4, 3, ...

LINKS

Robert Israel, Table of n, a(n) for n = 1..6866

EXAMPLE

a(7)=19; a(8)=20. 37 is the smallest number, larger than 20, that can be added to 20 and the result (57) is divisible by 19. So, a(9)=37.

MAPLE

A[1]:= 2: A[2]:= 3:

for n from 3 to 50 do

k:= -A[n-1] mod A[n-2];

A[n]:= k + A[n-2]*(1+floor((A[n-1]-k)/A[n-2]));

od:

seq(A[i], i=1..50); # Robert Israel, Oct 27 2019

CROSSREFS