A049525 I is the first, second, eighth, ... letter in this sentence not counting spaces or commas.

1, 2, 8, 19, 25, 41, 51, 56, 61, 66, 71, 76, 81, 86, 91, 103, 115, 120, 126, 131, 137, 142, 148, 164, 178, 201, 222, 238, 243, 259, 307, 323, 351, 367, 405, 410, 432, 446, 451, 494, 510, 515, 532, 555, 588, 615, 631, 636, 652, 664, 680, 691, 700, 712, 723, 734

Offset: 1

Author

J. Lowell

Keywords

• nonn
• word
• easy
• nice

Examples

			The sentence begins:
1234567890 1234567890 1234567890 1234567890 1234567890
Iisthefirs tsecondeig hthninetee nthtwentyf ifthfortyf
irstfiftyf irstfiftys ixthsixtyf irstsixtys ixthsevent
yfirstseve ntysixthei ghtyfirste ightysixth ninetyfirs
tonehundre dthirdoneh undredfift eenthonehu ndredtwent
iethonehun dredtwenty sixthonehu ndredthirt yfirstoneh
undredthir tyseventho nehundredf ortysecond onehundred ...
		

Crossrefs

Cf. A005224, A055508.

Programs

Mathematica

seed="iisthe";s[1]=1;s[2]=2; name[n_]:=
StringReplace[IntegerName[n,{"English","Ordinal"}],{"-"->""," "->""}];
s[n_]:=seed=StringJoin[seed<>name[StringPosition[seed,"i"][[n-2,1]]]];
l=s/@Range[56]; Table[StringPosition[Last[l],"i"][[k,1]],{k,1,Length[l]}]
(* Ivan N. Ianakiev, Apr 02 2022 *)

Python

from num2words import num2words
from itertools import islice
def n2w(n):
    os = num2words(n, ordinal=True).replace(" and", "")
    return os.replace(" ", "").replace("-", "").replace(chr(44), "")
def agen(): # generator of terms
    s, idx = "iisthe", 0
    while True:
        idx_rel = 1 + s.index("i")
        idx += idx_rel
        yield idx
        s = s[idx_rel:] + n2w(idx)
print(list(islice(agen(), 56))) # Michael S. Branicky, Apr 02 2022

Extensions

More terms from Robert G. Wilson v, Jul 18 2000

Corrected and extended by Larry Reeves (larryr(AT)acm.org), Nov 02 2000