a(n) is the sum of the divisors of n*2^n + 1.

Terms

a(0) =1a(1) =4a(2) =13a(3) =31a(4) =84a(5) =192a(6) =576a(7) =1344a(8) =2736a(9) =5040a(10) =13680a(11) =24276a(12) =56000a(13) =153842a(14) =308416a(15) =538920a(16) =1110276a(17) =2909040a(18) =5495040a(19) =14446080a(20) =31374720a(21) =45955008a(22) =106119552a(23) =233997312a(24) =527587200a(25) =1184932800a(26) =3247522560a(27) =4365239040a(28) =7784309910a(29) =16265125632