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 A171452 #15 May 09 2024 09:08:10 %S A171452 0,0,1,4,7,11,17,23,30,39,48,58,70,82,95,110,125,141,159,177,196,217, %T A171452 238,260,284,308,333,360,387,415,445,475,506,539,572,606,642,678,715, %U A171452 754,793,833,875,917,960,1005,1050,1096,1144,1192,1241,1292,1343,1395 %N A171452 a(n) = C(n,2) + floor(n/3). %C A171452 Exponents in Hankel transform A171451. %C A171452 For n>=2 a(n) is the smallest addend in the sums of n terms where all the natural numbers are used once 1+2=3, 4+5+6=15, 7+8+9+10=34, 11+12+13+14+16=66, 17+18+19+20+21+22=117 23+24+25+26+27+28+29=182, 30+31+32+33+35+36+37+38=272. - _Anton Zakharov_, Aug 28 2016 %H A171452 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,1,-2,1). %F A171452 G.f.: (1+2x)/((1-x)^3*(1+x+x^2)); %F A171452 a(n) = (3n^2-n-2)/6 + sqrt(3)*cos(2*Pi*n/3+Pi/6)/9 + sin(2*Pi*n/3+Pi/6)/3. %o A171452 (PARI) a(n)=n*(3*n-1)\6 \\ _Charles R Greathouse IV_, Aug 28 2016 %Y A171452 Cf. A130481 (first differences) %K A171452 easy,nonn %O A171452 0,4 %A A171452 _Paul Barry_, Dec 09 2009