A277972 a(1) = 1. a(n) is the smallest unlisted number, the name of which contains the first letter of the name of a(n-1) in English.

1, 2, 3, 8, 5, 4, 14, 15, 24, 10, 12, 13, 16, 6, 7, 17, 26, 18, 9, 11, 19, 20, 21, 22, 23, 25, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 64, 60, 61, 62, 63, 65, 66, 67, 68, 69

Offset: 1

Author

Ivan N. Ianakiev, Nov 07 2016

Keywords

• easy
• nonn
• word

Crossrefs

Cf. A277971.

Programs

Mathematica

name[n_]:=IntegerName[n,"Words"];a[1]=1;
a[n_]:=a[n]=Module[{i=1}, While[Or[MemberQ[Table[a[k],{k,1,n-1}],i],
!StringContainsQ[name[i],StringTake[name[a[n-1]],1]]],i++ ];i];
a/@Range[69] (* Ivan N. Ianakiev, Dec 20 2021 *)