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A308405 Numbers k such that k, when written in English, has 1 letter more than k+1. 0
3, 5, 8, 9, 14, 17, 23, 25, 28, 33, 35, 38, 43, 45, 48, 53, 55, 58, 63, 65, 68, 73, 75, 78, 83, 85, 88, 93, 95, 98, 103, 105, 108, 109, 114, 117, 123, 125, 128, 133, 135, 138, 143, 145, 148, 153, 155, 158, 163, 165, 168, 173, 175, 178, 183, 185, 188, 193, 195 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..59.

EXAMPLE

a(1) = 3 = THREE has 1 letter more than a(1) + 1 = FOUR;

a(2) = 5 = FIVE has 1 letter more than a(2) + 1 = SIX;

a(3) = 8 = EIGHT has 1 letter more than a(3) + 1 = NINE;

a(4) = 9 = NINE has 1 letter more than a(4) + 1 = TEN;

a(5) = 14 = FOURTEEN has 1 letter more than a(5) + 1 = FIFTEEN; etc.

PROG

(PARI) v1 = ["one", "two", "three", "four", "five", "six", "seven", "eight", "nine"];

v2 = ["eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"];

v3 = ["ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"];

conv(n) = {if (n >= 10^12, error("too big for this program"));

if (n >= 10^9, return (concat(concat(conv(n\10^6), "billion"), conv(n % 10^9))));

if (n >= 10^6, return (concat(concat(conv(n\10^6), "million"), conv(n % 10^6))));

if (n >= 10^3, return (concat(concat(conv(n\10^3), "thousand"), conv(n % 10^3))));

if (n >= 10^2, return (concat(concat(conv(n\100), "hundred"), conv(n % 100))));

if (n >= 20, return (concat(v3[n\10], conv(n%10))); );

if (n >= 10, if (n==10, return(v3[n\10]), return(v2[n % 10])); );

if (n, return(v1[n]), return (""));

} \\ after Michel Marcus in A303475

is(n) = #conv(n)-1==#conv(n+1) \\ Felix Fröhlich, May 25 2019

CROSSREFS

Sequence in context: A137319 A138808 A185456 * A018804 A032682 A022769

Adjacent sequences:  A308402 A308403 A308404 * A308406 A308407 A308408

KEYWORD

nonn,word

AUTHOR

Eric Angelini, May 25 2019

EXTENSIONS

17 and terms beyond 98 from Felix Fröhlich, May 25 2019

STATUS

approved

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Last modified November 18 17:21 EST 2019. Contains 329287 sequences. (Running on oeis4.)