This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A090580 #10 Jul 08 2019 15:53:30 %S A090580 1,5,15,35,70,126,210,330,495,714,992,1330,1725,2170,2654,3162,3675, %T A090580 4170,4620,4998,5283,5460,5520,5460,5283,4998,4620,4170,3675,3162, %U A090580 2654,2170,1725,1330,992,714,495,330,210,126,70,35,15,5,1 %N A090580 Number of numbers with 5 decimal digits and sum of digits = n. %C A090580 There are 90000 numbers with 5 decimal digits, the smallest being 10000 and the largest 99999. %F A090580 G.f.: (x - x^10)/(1 - x)*((1 - x^10)/(1 - x))^4. - _Michael De Vlieger_, Dec 07 2016 %e A090580 a(2)=5: 10001, 10010, 10100, 11000, 20000. %t A090580 Rest@ CoefficientList[Series[(x - x^10)/(1 - x) ((1 - x^10)/(1 - x))^4, {x, 0, 45}], x] (* or *) %t A090580 Function[w, Count[w, #] & /@ Range[Max@ w]]@ Map[Total@ IntegerDigits@ # &, Range[10^#, 10^(# + 1) - 1]] &@ 4 (* _Michael De Vlieger_, Dec 07 2016 *) %t A090580 Tally[Total[IntegerDigits[#]]&/@Range[10000,99999]][[All,2]] (* _Harvey P. Dale_, Jul 08 2019 *) %o A090580 (PARI) b=vector(45,i,0);for(n=10000,99999,a=eval(Vec(Str(n)));b[sum(j=1,5,a[j])]++);for(n=1,45,print1(b[n],",")) - Herman Jamke (hermanjamke(AT)fastmail.fm), Oct 19 2006 %Y A090580 Cf. A071817 3-digit numbers, A090579 4-digit numbers, A090581 6-digit numbers. %K A090580 base,fini,full,nonn %O A090580 1,2 %A A090580 _Hugo Pfoertner_, Jan 12 2004