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 A099610 a(n) is the smallest odd number that is greater than n^2 and is the product of two distinct primes. 3
 15, 15, 15, 21, 33, 39, 51, 65, 85, 111, 123, 145, 177, 201, 235, 259, 291, 327, 365, 403, 445, 485, 533, 579, 629, 679, 731, 785, 843, 901, 965, 1027, 1099, 1157, 1227, 1299, 1371, 1457, 1527, 1603, 1685, 1765, 1851, 1937, 2031, 2117, 2215, 2305, 2407, 2501, 2603, 2705, 2811, 2921, 3027, 3139, 3261, 3365, 3487, 3601, 3737, 3845, 3973, 4097, 4227, 4359, 4497, 4627 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A099611(n) < A000290(n) < a(n); subsequence of A046388. This is an "arithmetic" sequence (like sigma(n)), so it has offset 1. - N. J. A. Sloane, Dec 06 2021 LINKS N. J. A. Sloane, Table of n, a(n) for n = 1..10000 MAPLE with(numtheory); A099610 := proc(n) local M, i, t1, tt; M:=100; t1:=n^2; for i from 1 to M do tt:=t1+i; if (tt mod 2) = 1 and tau(tt) = 4 and nops(factorset(tt)) = 2 then return(tt); fi; od: lprint("error: the internal parameter M needs to be increased"); end proc; # N. J. A. Sloane, Dec 05 2021 MATHEMATICA Module[{nn=70, p2p}, p2p=Union[Times@@@Subsets[Prime[Range[ 2, PrimePi[ Ceiling[ nn^2/3]]]], {2}]]; Table[SelectFirst[p2p, #>n^2&], {n, nn}]] (* Harvey P. Dale, Dec 06 2021 *) PROG (Python) from itertools import count from sympy import factorint def A099610(n): for i in count(n**2+(n%2)+1, 2): fs = factorint(i) if len(fs) == 2 == sum(fs.values()): return i # Chai Wah Wu, Dec 05 2021 CROSSREFS Cf. A000290, A046388, A099611, A349806 (a(n)-n^2). Sequence in context: A346623 A225917 A140806 * A085321 A239315 A003890 Adjacent sequences: A099607 A099608 A099609 * A099611 A099612 A099613 KEYWORD nonn AUTHOR Reinhard Zumkeller, Oct 25 2004 EXTENSIONS Edited and corrected by Harvey P. Dale and N. J. A. Sloane, Dec 05 2021 STATUS approved

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Last modified April 14 20:39 EDT 2024. Contains 371667 sequences. (Running on oeis4.)