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A088613 Smallest nonsquarefree multiple of n. 1
4, 4, 9, 4, 20, 12, 28, 8, 9, 20, 44, 12, 52, 28, 45, 16, 68, 18, 76, 20, 63, 44, 92, 24, 25, 52, 27, 28, 116, 60, 124, 32, 99, 68, 140, 36, 148, 76, 117, 40, 164, 84, 172, 44, 45, 92, 188, 48, 49, 50, 153, 52, 212, 54, 220, 56, 171, 116, 236, 60, 244, 124, 63, 64, 260, 132 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
If n is nonsquarefree, then a(n) = n. If n is an even squarefree integer, then a(n) = 2*n. If n is an odd squarefree multiple of 3, then a(n) = 3*n. If n is a squarefree integer not divisible by either 2 or 3, then a(n) = 4*n. a(p) = 4p if p is a prime >= 5. - Leroy Quet, May 14 2008
Sum_{k=1..n} a(k) ~ c * n^2, where c = 1/2 + 13/(2*Pi^2) = 1.158587... . - Amiram Eldar, Jul 02 2023
MATHEMATICA
snmn[n_]:=Which[!SquareFreeQ[n], n, EvenQ[n], 2n, Mod[n, 3]==0, 3n, True, 4n]; Array[snmn, 70] (* Harvey P. Dale, Nov 11 2020 *)
CROSSREFS
Cf. A013929.
Sequence in context: A023405 A160900 A035116 * A351582 A049723 A010661
KEYWORD
easy,nonn
AUTHOR
Amarnath Murthy, Oct 16 2003
EXTENSIONS
More terms from Ray Chandler, Oct 18 2003
STATUS
approved

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Last modified March 2 21:08 EST 2024. Contains 370498 sequences. (Running on oeis4.)