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!)
 A112562 Sieve performed by successive iterations of steps where step m is: keep m terms, remove the next 4 and repeat; as m = 1,2,3,.. the remaining terms form this sequence. 4
 1, 6, 31, 96, 241, 546, 1171, 1776, 2761, 5046, 7591, 11856, 19021, 20706, 31711, 44016, 60481, 71946, 92191, 120216, 138601, 181986, 226831, 302496, 379381, 400686, 487831, 574656, 704461, 831606, 1029631, 1092936, 1333321, 1462146 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Formula: a(n) = 1 + [..[[[[n*2/1]3/2]4/3]5/4]...(k+1)/k]...] where denominators k of the fractions used in the product vary over all natural numbers not congruent to 0 (mod 5); thus the product will eventually reach a maximum value of a(n). LINKS FORMULA a(n) = 1 + 5*A073362(n). EXAMPLE Sieve starts with the natural numbers: 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,... Step 1: keep 1 term, remove the next 4, repeat; giving 1,6,11,16,21,26,31,36,41,46,51,56,61,66,... Step 2: keep 2 terms, remove the next 4, repeat; giving 1,6,31,36,61,66,91,96,121,126,151,156,... Step 3: keep 3 terms, remove the next 4, repeat; giving 1,6,31,96,121,126,211,216,241,306,331,... Continuing in this way, we obtain this sequence. Using the floor function product formula: a(2) = 1 + [..[(2)*2/1]*3/2]*4/3]*6/5]*7/6]*8/7]*10/9]* 11/10]*12/11]*14/13]*15/14]*16/15]*18/17]*19/18]*20/19] = 21. PROG (PARI) {a(n)=local(A=n, B=0, k=0); until(A==B, k=k+1; if(k%5==0, k=k+1); B=A; A=floor(A*(k+1)/k)); 1+A} CROSSREFS Cf. A073362, A112560, A112561, A112563, A112564, A112565, A112566, A112567, A112568, A112569. Sequence in context: A087725 A273790 A096959 * A244716 A024447 A303172 Adjacent sequences:  A112559 A112560 A112561 * A112563 A112564 A112565 KEYWORD nonn AUTHOR Paul D. Hanna, Oct 14 2005 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 February 16 21:31 EST 2020. Contains 331975 sequences. (Running on oeis4.)