cp's OEIS Frontend

A247468 Smallest number m such that A247462(m) = n.

%I A247468 #7 Feb 09 2022 09:04:50
%S A247468 1,5,164,501,7364,29121,515504,2445693,92781321
%N A247468 Smallest number m such that A247462(m) = n.
%F A247468 A247462(a(n)) = n and A247462(m) < n for m < a(n).
%e A247468 .  n |    a(n) |                  A058977 trajectory
%e A247468 . ---+---------+---------------------------------------------------------
%e A247468 .  2 |       5 | 1/a(2)-5/2-7
%e A247468 .  3 |     164 | 1/a(3)-19/3-13/2-4
%e A247468 .  4 |     501 | 1/a(4)-253/2-25/3-9/2-11
%e A247468 .  5 |    7364 | 1/a(5)-499/3-253/2-25/3-9/2-11
%e A247468 .  6 |   29121 | 1/a(6)-14563/2-979/3-493/2-19/3-13/2-4
%e A247468 .  7 |  515504 | 1/a(6)-34375/3-17191/2-535/3-271/2-23/3-15/2-17
%e A247468 .  8 | 2445693 | 1/a(8)-1222849/2-58241/3-14563/2-979/3-493/2-19/3-13/2-4
%o A247468 (Haskell)
%o A247468 import Data.List (elemIndex); import Data.Maybe (fromJust)
%o A247468 a247468 = (+ 1) . fromJust . (`elemIndex` a247462_list)
%o A247468 (PARI) f2(p, q) = my(f=factor(p+q)[, 1]~); vecsum(f)/#f;
%o A247468 f1(r) = f2(numerator(r), denominator(r));
%o A247468 loop(list) = {my(v=Vecrev(list)); for (i=2, #v, if (v[i] == v[1], return(1)); ); }
%o A247468 f(n) = {my(ok=0, m=f2(n, 1), list=List(), nb=1); while(denominator(m) != 1, m = f1(m); nb++; listput(list, m); if (loop(list), return (0)); ); return(nb); } \\ A247462
%o A247468 a(n) = my(k=1); while(f(k) != n, k++); k; \\ _Michel Marcus_, Feb 09 2022
%Y A247468 Cf. A247462, A058977.
%K A247468 nonn,more
%O A247468 1,2
%A A247468 _Reinhard Zumkeller_, Sep 17 2014
%E A247468 a(9) from _Michel Marcus_, Feb 09 2022