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A359035 a(n+1) is the smallest number not already used which can be written as the product of two numbers with the same difference as a(n) and a(n-1); a(1)=1 and a(2)=2. 3
1, 2, 6, 5, 12, 8, 21, 14, 18, 32, 15, 38, 24, 51, 28, 50, 23, 58, 36, 48, 13, 74, 62, 45, 60, 16, 92, 77, 34, 44, 11, 70, 122, 53, 142, 90, 108, 19, 182, 164, 40, 125, 86, 82, 96, 72, 25, 98, 150, 165, 54, 112, 59, 110, 52, 120, 69, 106, 78, 29, 102, 228, 127, 206, 80, 256, 177, 162 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
This sequence starts chaotic but makes a sudden transition into a linear recurrence for n > 433. For details see the formula section. - Thomas Scheuerle, Dec 13 2022
LINKS
Neal Gersh Tolunsky, Table of n, a(n) for n = 1..600
FORMULA
From Thomas Scheuerle, Dec 13 2022: (Start)
a(534+(k+1)*3) = 2*a(534+k*3)-1 for k >= 0 and a(534) = 555.
a(535+(k+1)*3) = 2*a(535+k*3)+1 for k >= 0 and a(535) = 2214.
a(536+(k+1)*3) = 2*a(536+k*3)+2 for k >= 0 and a(536) = 3322. (End)
EXAMPLE
a(3) is 6: The difference between the two previous terms is 1 and 2*3=6 is the smallest number that is the product of two numbers with a difference of 1.
PROG
(MATLAB)
function a = A359035( max_n )
a = [1 2];
for n = 3:max_n
m = 1; d = abs(a(n-1)-a(n-2));
while ~isempty(find(a==(m*(m+d)), 1))
m = m+1;
end
a(n) = m*(m+d);
end
end % Thomas Scheuerle, Dec 13 2022
CROSSREFS
Cf. A002378.
Sequence in context: A092744 A077174 A211201 * A179627 A193977 A092313
KEYWORD
nonn
AUTHOR
Neal Gersh Tolunsky, Dec 12 2022
STATUS
approved

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Last modified July 24 20:30 EDT 2024. Contains 374585 sequences. (Running on oeis4.)