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A356371 a(n) is the smallest positive integer k, such that set of pairwise gcd of k, k+1, ..., k+n has a cardinality of n. 3
1, 2, 3, 8, 15, 24, 35, 48, 63, 270, 440, 528, 780, 1078, 2925, 1440, 8160, 2142, 5472, 34560, 23919, 235598, 64239, 42480, 158400, 1255800, 1614600, 1247400, 16442971, 8233650, 41021370, 21561120, 127327167, 439824000, 439824000, 24504444, 1329112224, 1653775162 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
n | a(n). - David A. Corneth, Oct 17 2022
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..60 (first 42 terms from Chai Wah Wu)
MATHEMATICA
a[n_] := Module[{k = 1}, While[Length[Union[GCD @@@ Subsets[k + Range[0, n], {2}]]] != n, k++]; k]; Array[a, 20] (* Amiram Eldar, Oct 17 2022 *)
PROG
(Python)
from math import gcd
from itertools import count
def A356371(n):
for k in count(n, n):
if len(set(gcd(i, j) for i in range(k, n+k+1) for j in range(i+1, n+k+1))) == n:
return k # Chai Wah Wu, Oct 18 2022
CROSSREFS
Cf. A214799.
Sequence in context: A122412 A365413 A174019 * A293389 A128035 A003473
KEYWORD
nonn
AUTHOR
Gleb Ivanov, Oct 17 2022
EXTENSIONS
a(31)-a(38) from Giovanni Resta, Oct 17 2022
STATUS
approved

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Last modified May 19 14:45 EDT 2024. Contains 372698 sequences. (Running on oeis4.)