A339700 a(n) is the n-th nonnegative number to light exactly n segments when displayed on a calculator.

71, 77, 47, 61, 70, 52, 62, 99, 136, 190, 246, 263, 306, 589, 882, 1085, 1838, 2059, 2308, 2869, 5886, 8689, 10800, 18098, 20268, 20896, 28608, 58880, 86886, 106898, 180889, 200858, 208698, 283888, 588868, 868880, 1068889, 1808886, 2008086, 2086868, 2809888, 5888808, 8688868, 10688886, 18088880

Offset: 5

Author

Graham Holmes, Dec 13 2020

Keywords

• nonn
• base

Comments

a(n) is undefined for n<5, as there are no numbers with 1 segment, 1 with 2 segments, 1 with 3 segments, and 2 with 4 segments. If 0 is excluded as a valid input - so the series would refer to "the n-th positive number" - then a(6) would be 111 rather than 77.

Examples

			For n=7, 47 is the 7th positive number to light 7 segments, after 8, 12, 13, 15, 21, and 31.
		

Links

• Graham Holmes, Table of n, a(n) for n = 5..82
• Index entries for sequences related to calculator display

Crossrefs

Cf. A006942 (segments lit), A216261, A331529.

Programs

JavaScript

s=[6,2,5,5,4,5,6,3,7,6];p=[];a=[];for(i=2;i<=100;i++)p[i]=0;for(i=1;i<=1000000;i++){d=i;n=0;do{x=d%10;n+=s[x];d=(d-x)/10;}while(d>0)p[n]++;if(p[n]==n)a[n]=i;}for(c=2;c<=40;c++)document.write(c+": "+a[c]+"
");