The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A322493 Start of first occurrence of n consecutive odd squarefree composite numbers. 1
 15, 33, 91, 213, 213, 893, 893, 1343 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The sequence is finite because among 9 or more consecutive odd numbers there is always a multiple of 3*3. - Rémy Sigrist, Dec 19 2018 LINKS EXAMPLE a(1) = 15 = A024556(1). a(2) = 33 because 33 = 3*11 and 35 = 5*7 is the smallest pair of odd squarefree composite numbers. 31 and 37 are prime. a(8) = 1343: 1343=17*79, 1345=5*269, 1347=3*449, 1349=19*71, 1351=7*193, 1353=3*11*41, 1355=5*271, 1357=23*59, whereas 1341=3^2*149 and 1359=3^2*151 are not squarefree. MATHEMATICA a[n_] := For[k = 1, True, k = k+2, If[AllTrue[Range[k, k+2(n-1), 2], CompositeQ[#] && SquareFreeQ[#]&], Return[k]]]; Array[a, 8] (* Jean-François Alcover, Dec 31 2018 *) CROSSREFS Cf. A024556, A321617. Sequence in context: A108517 A211327 A222179 * A190052 A242243 A219855 Adjacent sequences:  A322490 A322491 A322492 * A322494 A322495 A322496 KEYWORD nonn,fini,full AUTHOR Hugo Pfoertner, Dec 19 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 22 06:39 EDT 2021. Contains 345373 sequences. (Running on oeis4.)