cp's OEIS Frontend

A228442 Ending letter of a(n) equals starting letter of a(n+1), when spelled out in German; always choose the smallest possible number not yet used and not ending the sequence.

%I A228442 #17 Dec 23 2024 14:53:43
%S A228442 1,6,7,9,19,900,1000,13,901,16,905,5,15,906,17,907,908,1001,600,1005,
%T A228442 500,1006,601,605,501,606,607,909,910,911,505,506,608,1007,912,57,913,
%U A228442 914,915,916,917,918,919,9000,300,1008,1009,9001,609,9005,508,1010,9006,610,9007
%N A228442 Ending letter of a(n) equals starting letter of a(n+1), when spelled out in German; always choose the smallest possible number not yet used and not ending the sequence.
%C A228442 German version of A227865, a variant of A230862 without monotonicity.
%C A228442 We use "tausend" rather than "eintausend", in order to allow numbers ending in "t", like "hundert" and "acht".
%H A228442 E. Angelini, <a href="https://web.archive.org/web/*/http://list.seqfan.eu/oldermail/seqfan/2013-November/011824.html">Re: A sequence in your style</a>, SeqFan list, Nov 01 2013
%H A228442 <a href="/index/Ge#German">OEIS Index entries for sequences related to German names of numbers</a>
%e A228442 EinS, SechS, SiebeN, NeuN, NeunzehN, NeunhunderT, TausenD, DreizehN, NeunhunderteinS, SechzehN, NeunhundertfünF, FünF, FünfzehN, NeunhundertsechS, SiebzehN, NeunhundertsiebeN, NeunhundertachT, TausendeinS, SechshunderT, TausendfünF, FünfhunderT, TausendsechS, SechshunderteinS, SechshundertfünF, FünfhunderteinS, SechshundertsechS, SechshundertsiebeN, NeunhundertneuN, NeunhundertzehN, NeunhundertelF, FünfhundertfünF, FünfhundertsechS, SechshundertachT, TausendsiebeN, NeunhundertzwölF, FünfhundertsiebeN, NeunhundertdreizehN, NeunhundertvierzehN, NeunhundertfünfzehN, NeunhundertsechzehN, NeunhundertsiebzehN, NeunhundertachtzehN, NeunhundertneunzehN, NeuntausenD, DreihunderT, TausendachT, TausendneuN, NeuntausendeinS, SechshundertneuN, NeuntausendfünF, FünfhundertachT, TausendzehN, NeuntausendsechS, SechshundertzehN, NeuntausendsiebeN, ...
%o A228442 (PARI) /* Warning: Beyond n=150, the script may yield wrong results.*/
%o A228442 {A228442(Nmax, letters=Vec("dfnst"), values=[[3, 13], [5, 15], [9, 19], [6, 7, 16, 17], [10]],counter=[-1, 0, 0, 0, -1])= my(ok(n)=setsearch(letters, Vec(n=German(n))[#n]),a,ini,i); vector(Nmax,k, a=if(k>1, if(counter[i=setsearch(letters, ini=Vec(a=German(a))[#a])]>0, until(ok(counter[i]++), counter[i]%100<20&&next; Vec(German(counter[i]+=80))[1] != ini && counter[i] = values[i][1]*1000; break); counter[i], if(-counter[i]-->#values[i], counter[i]=values[i][1]*100, values[i][-counter[i]] )),1))} /* see A007208 for German() and A227865 for spellout() if you wish to capitalize initial and final letters */
%Y A228442 Cf. A227865, A230862.
%K A228442 nonn,word
%O A228442 1,2
%A A228442 _M. F. Hasler_, Nov 02 2013