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 A332989 a(n) is the smallest number writable in n different ways as the sum of two distinct nonzero pentagonal numbers. 3
 6, 211, 2999, 13352, 205427, 250927, 1134927, 2177527, 5002427, 6422352, 17349697, 30135652, 45997927, 55075502, 168570052, 130917177, 101275552, 249483677, 441561407, 433742427, 771789552, 1546505052, 1316582177, 1701923302, 2288827477, 1073520852, 3110207127 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS I conjecture this sequence is infinite. LINKS Giovanni Resta, Table of n, a(n) for n = 1..40 EXAMPLE 211 can be written 35 + 176 and 1 + 210; 2999 can be written 852 + 2147, 247 + 2752, 117 + 2882; 13352 = P(52) + P(79) = P(29) + P(90) = P(17) + (93) = P(10) + P(94). PROG (PARI) a(n) = for(k=1, oo, if(sum(i=1, sqrt(1+12*k)\6, sqrt(1+24*k+12*i-36*i*i)%6==5)==n, return(k))); \\ Jinyuan Wang, Mar 06 2020 CROSSREFS Cf. A000326, A332988. Cf. A093195 (analog sequence for perfect squares). Sequence in context: A073100 A093536 A002037 * A030265 A275567 A007221 Adjacent sequences:  A332986 A332987 A332988 * A332990 A332991 A332992 KEYWORD nonn AUTHOR Olivier Gérard, Mar 05 2020 EXTENSIONS Name clarified by Jinyuan Wang, Mar 06 2020 Terms a(12) and beyond from Giovanni Resta, Mar 08 2020 STATUS approved

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Last modified May 29 10:41 EDT 2020. Contains 334699 sequences. (Running on oeis4.)